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Section III. IMPROVISED SHELTERS
3-13. Requirement for Improvised Shelters
a. There are many occasions when tents or other regular shelters are not available. In summer, if the weather is mild, individuals may need protection only from insects. In winter, however, individuals cannot stay in the open for long periods unless they are moving. The requirements for improvised shelters may arise for several reasons, e.g., vehicles carrying tents may be unable to reach the troops due to difficult terrain or enemy action. In case of emergency, each individual must know how to protect himself from the effects of the weather.
b. If suitable natural shelters such as caves or rock shelves are available, they should be used. If natural shelters are not available, a temporary improvised shelter must be established.
c. The type of improvised shelter to be built depends on the equipment and materials available By the proper use of materials available, some sort of shelter can be built during any season of the year. In open terrain a shelter can be built using ponchos, canvas, snowblocks, or other materials. Snow caves, snow trenches, or snow holes may be constructed in the winter if the snow is both deep and well-compacted. In the woods, a lean-to is normally
preferable to other types of shelter. In northern areas, nature provides the individual with the means to prepare a shelter. His comfort, however, greatly depends on his initiative and skill at improvising.
d. A shelter should always provide adequate protection from the elements, retain heat, have suitable ventilation, and provide drying facilities.

3-14. Poncho Shelters
A poncho is a part of an individual’s uniform. It is a multipurpose piece of equipment that may be used as a rain garment, a waterproof bedcover, a ground sheet, or a shelter. The simplest type of shelter can be made by merely pulling the poncho over the sleeping bag. For additional comfort, various types of shelters and lean-tos may be made by attaching ponchos to trees, tree branches or poles.
a. One-Man Shelter. A one-man shelter (fig. 3-9) may be made from one poncho. The poncho is spread, hood side up, on the ground, and the hood opening is tightly closed by adjusting and typing the hood drawstrings. The poncho is raised at the middle of its short dimension to form a ridge, and then staked out at the corners and sides. Side stakes should not be driven through the grommets at the corners or sides, because this may tear the poncho. A short piece of rope is tied to the grommets and, in turn, to the stakes. Snow, sod, or boughs are used to seal two sides and one end of the shelter to provide additional protection from the wind and to retain heat inside the shelter.
b. Two-Man Shelter. To construct a two-man shelter (fig. 3-9), ponchos are spread on the ground, hood side up, with the long sides together so that the snap fastener studs of one poncho may be fastened to the snap fastener sockets of the other poncho. Hood openings must be tightly closed by adjusting and tying the hood drawstrings. Ponchos are raised where they are joined to form a ridge; ropes are then attached to grommets at the ends of the ridge and run over forked sticks. The shelter tent is then staked out at the corners and sides, as described in a above. A third poncho may be snapped into the other ponchos to form a ground cloth.
Figure 3-9

3-15. Lean-To
a. Materials. The lean-to shelter, used in forested areas, is constructed of trees and tree limbs. String or wire helps in the building, but is not necessary. A poncho, a piece of canvas, tarpaulin, or a parachute, in addition to the boughs, may be used for covering.
Figure 3-10
b. Size. The lean-to is made to accommodate a variable number of individuals. It may be built for one man only, teams, gun crews, patrols, or similar small groups. From a practical point of view, a rifle squad is the largest element to be sheltered in one double lean-to.
c. Types. Depending on the number of individuals to be sheltered, two types of lean-tos, single and double, are used.
d. Construction.
(1) Single lean-to (fig. 3-10). To save time and energy, two trees of appropriate distance apart, and sturdy enough to support the crosspiece approximately 1.50 meters (5') off the ground, are selected when operating in forested areas. It may be necessary to cut two forked poles of desired height, or construct two A-frames to hold the crosspieces, or use a combination of these supports when bivouacking in sparse wooded or semi-open
areas. A large log is then placed to the rear of the lean-to for added height. Other methods that may be used are packing the snow down or using snowblocks instead of a heavy log. Stringers approximately 3 meters (10') long and 5 to 8 centimeters (2" to 3") in diameter are then placed, approximately 46 cm (18") apart, from the crosspiece over the top of the log in the rear of the shelter. Material such as cardboard, canvas or ponchos may be placed over the framework to preclude falling or melting snow, warmed by the fire, from dropping through. One or both sides of the lean-to and the roof are then thatched.
(2) Double lean-to (fig. 3-11). Two single lean-tos are built facing each other and approximately 1.50 to 2 meters (5' to 6') apart. The space between single lean-tos must be sufficient to permit the occupants to move freely around the log fire placed along the centerline of this space and to allow the smoke to get out through the opening instead of gathering under the roofing. If desired, one end of the middle space may be covered by a wall made of boughs or other materials for additional protection from the draft and wind.
Figure 3-11
e. Heating. In heating a lean-to, any kind of oven fire may be used. The best type for large size lean-tos, however, is the log fire, so the heat will be evenly distributed over the entire length of the lean-to, see paragraph 3-21 d. In employing open fires for heating, precautions must be taken to prevent the fire from burning too hot and burning down the shelter or setting the roof on the with sparks.

3-16. Tree Shelter
a. Tree-Pit Shelter. In wooded areas, the deep snow and tree-pit shelter (fig. 3-12) furnishes temporary protection. To construct a tree-pit shelter a large tree is selected with thick lower branches and surrounded with deep snow. The snow is shaken from the lower branches and the natural pit is enlarged
around the trunk of the tree. The walls and floor are then lined with branches and the roof thickened. Canvas or other material on hand may be used for the roof.
Figure 3-12
b. Fallen Tree Shelter. An emergency shelter for one man can be constructed by cutting down a coniferous tree at a point about one meter (3') from the ground. The underside is trimmed and the cut material placed on the ground to provide insulation. This shelter will provide some protection from the elements for a man in his sleeping bag. Another way to build this shelter is to tie a pole to a tree and drape a poncho or similar material over the pole.

3-17. Wigwam
A conventional wigwam or tepee can be built in wooded areas by typing a number of poles near the top and spreading them at the bottom to form a large circle. This framework is then covered with available tree boughs, canvas, cardboard, or other suitable material.

3-18. Snow Wall
In open terrain with snow and ice, a snow wall (fig. 3-13) may be constructed for protection from strong winds. Blocks of compact snow or ice are used to form a windbreak.
Figure 3-13

3-19. Snow Hole
A snow hole (fig. 3-14) provides shelter quickly. It is constructed by burrowing into a snowdrift or by digging a trench in the snow and making a roof of ponchos and ice or snowblocks supported by skis, ski poles or snowshoes. A sled provides excellent insulation for the sleeping bag. Boughs, if available, can be used for covering the roof and for the bed.
Figure 3-14

3-20. Snow Cave
a. Location. A snow cave (figs. 3-15 and 3-16) can be used as an improvised shelter in the open areas where deep and compacted snow is available. Normally, a suitable site is located on the lee side of a steep ridge or riverbank where drifted snow accumulates in unusual depths.
b. Basic Construction Principles. Basic principles for construction of all snow caves are as follows:
(1) The tunnel entrance must give access to the lowest level of the chamber, which is the bottom of the pit where cooking is done and equipment is stored.
(2) The snow cave must be high enough to provide comfortable sitting space.
(3) The sleeping areas must be on a higher level than the highest point of the tunnel entrance so that the rising warm air will permit the men to sleep more comfortably.
(4) The roof must be arched both for strength and so that drops of water forming on the inside will not fall on the floor, but will follow along the curved sides, glazing over the walls when frozen.
(5) The roof must be at least 30 cm (1') thick.
c. Size. The size of the snow cave depends upon the number of men expected to occupy it. A large cave is usually warmer and more practical to construct and maintain than several small caves. In good snow conditions a 16- to 20-man cave is the most practical. d. Shape. The shape of the snow cave can be
varied to suit conditions. When the main cave is built, short side tunnels are dug to make one- or two-man sleeping rooms, storage space, latrine and kitchen space.
e. Construction. The following steps should be observed in construction:
(1) A deep snowdrift at least 243 cm (8') deep is located. Newly fallen, powdery or loose snow should be avoided.
(2) The depth of a snowdrift may be tested with a sharpened sapling approximately 365 cm (12') in length, or in the absence of trees the shorter ski pole or avalanche probe (The availability of an avalanche probe is discussed in FM 31-72.)
Figure 3-15 Figure 3-16
(3) The entrance is chosen carefully so the wind will not blow into the cave or the entrance become blocked by drifting snow.
(4) A small tunnel is burrowed directly into the side of the drift for one meter (3'). A chamber is excavated from this tunnel.
(5) Excavation is done to the right and left so that the length of the chamber is at right angles to the tunnel entrance.
(6) Due to the fact that the individuals digging will become wet, they should wear the minimum amount of clothing possible to insure that they have a change of dry clothing upon completion of the task.
f. Heating and Safety Measures. The cave can be heated with the one-burner gasoline stove or with candles. The fires should be extinguished when individuals are sleeping, thus reducing the danger of fire and asphyxiation. If the weather is severe and it becomes necessary to keep a fire going while the individuals are asleep, an alert fire guard must be posted in each cave. The ventilation holes must be inspected every 2 or 3 hours to insure that they
have not become clogged by snow or by icing.
g. Insulation. To insure that the cave is warm, the entrance should be blocked with a rucksack, piece of canvas, or snowblock when not in use. All available material, such as ponchos, cardboard, brush, boughs, etc., should be used for ground insulation.
h. Other Precautions. Walking on the roof may cause it to collapse. At least two ventilators, one in the door and one in the roof, are used. A ski pole can be stuck through the roof ventilator to clear it from the inside. Extra care must be exercised to keep air in the cave fresh when heating or cooking. The entrance should be marked by placing a pair of skis or other equipment upright on each side of the entry way.

3-21. Campfires
a. Matches and Fire Starters. A supply of matches in a waterproof container, heat tablets, or fire starters must be carried by all individuals operating in cold weather. They are a necessity, especially where snow and ice add to the problems of securing tinder for starting a fire. In emergencies, matches should be used sparingly and lighted candles used to start fires whenever possible, or if available, a little engine oil will help ignite wet or frozen wood without the flash hazard of the more volatile petroleum fuels. As a safety precaution, it should be remembered that fire starters are extremely inflammable and must be kept away from open flames and heat.
b. Selecting Site. Individuals building a fire in the field should carefully select a site where the fire is protected from the wind. Standing timber or brush makes a good windbreak in wooded areas, but in open country some form of protection must be provided. A row of snowblocks, the shelter of a ridge, or a scooped-out side of a snowdrift will serve as a windbreak on barren terrain.
c. Starting and Maintaining Fire. Before using matches, a supply of tinder must be on hand. The use of heat tablets is recommended for the safe starting of fires. In inclosed areas, gasoline or other high inflammable fire starters will not be used. In the open, and under very strict control, small quantities of gasoline may be used to start fires when other means are not available. Many types of fuel are available for fires. The driest wood is found in dead, standing trees. Fallen timber may often be wet and less suitable. In living trees, branches above snow level are the driest. Green and frozen trees are generally not suitable because they will not burn freely. Splitting green willows or birches into small pieces provides a fairly good method of starting and maintaining a fire, if no deadwood is available. Also, dry grass, birchbark, and splits of spruce bark with pitch tar are excellent fire starters. It is good practice to secure a sufficient amount of firewood to last throughout the night, before retiring.
d. Types of Fire. Any kind of open fire may be used with most of the improvised shelters. In deep snow, a fire base (fig. 3-17) of green wood should be built first to protect the campfire from sinking into the snow. For a single lean-to or snow wall, afire reflector (fig. 3-10) may be built of green logs or poles to reflect the heat into the shelter and to serve as a steadily. The most suitable types for single and double lean-tos are the log fires (fig. 3-18).
(1) Two, preferably three, logs are used for this type of campfire. Dry, hardwood logs, if possible, 20 to 40 cm (approx 1') in diameter and approximately
the same length as the lean-to are selected and brought to the fire site. First, two logs are place side by side on small green blocks to support them above the snow or ground for a better draft. Then the third log is placed in the middle and on the top of the other two logs. For better burning, the surfaces of logs which face each other are chipped. Before lighting the fire, small wedges are placed between the chipped surfaces of the logs for better draft. Fire is
then started at several places to help it spread the entire length of the logs. A log fire of this type will burn all night with only minimum care.
(2) When only two logs are used, four vertical stakes must be driven into the snow to keep one log on top of the other. A disadvantage of this type of log fire is the fact that the vertical stakes tend to give way when the snow starts melting around the fire.
Figure 3-17 Figure 3-18

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