EN0065 Lesson 4 Practice Exercise Answer Key

LESSON 4

SELF TEST

ANSWER KEY AND FEEDBACK

1. In which use of barbed wire is each series of concertinas placed about 10 meters in depth?

A series of barbed wire concertinas should be placed about 10 meters in depth to construct a roadblock to stop wheeled vehicles.

2. How many more meters of barbed wire are on a full reel than are put on a bobbin?

Barbed wire is issued in reels of 400 meters of wire. It is taken off the reels and put on bobbins with 30 meters of wire on each when used to repair entanglements or build short lengths of fence. Thus, 400 meters of wire on a reel and 30 meters on a bobbin is a difference of 370 meters (more barbed wire on a full reel than on a bobbin).

3. What advantage does barbed tape have over standard barbed wire?

Barbed tape weighs one-third as much as equal lengths of standard barbed wire.

4. Why are the U-shaped steel pickets used to support wire entanglements emplaced with the hollow surface (concave side) facing enemy fire?

U-shaped steel pickets are driven with the hollow surface (concave side) facing enemy fire because enemy small arms projectiles ricochet from convex sides and may cause casualties.

5. In which direction should fence-building operations normally proceed?

All fence-building operations normally proceed from right to left, as one faces the enemy.

6. How and why are the ends of the wire on bobbins marked?

A piece of white tracing tape should be tied to the end of the wire on each bobbin or reel to facilitate finding it.

7. When a standard barbed wire concertina is being collapsed for transportation or storage, what keeps the bottom of the wire coil from fanning out?

To close a concertina, one man at each end places a foot at the bottom of the coil to keep it from fanning out while they walk toward each other to compress the concertina.

8. Which kind of picket is recommended for the construction of wire entanglement in combat areas in close proximity to the enemy?

Screw pickets should be used when constructing wire entanglements in proximity to the enemy. These pickets can be installed with less noise.

9. In the construction of barbed wire entanglements, which tie is used to join two wires that cross?

The apron tie is used to tie together two wires that cross. It is tied in the same way as the post tie, except that the apron tie is a wire-to-wire tie and the post tie is a wire-to-post tie.

10. In the construction of a four-strand cattle fence, which fence construction team installs the third strand from the top?

Barbed wires of a four-strand cattle fence are installed from the bottom up. The first team which has been organized for this work puts on the bottom wire and team 2 installs the second wire from the bottom (third wire from the top).

11. What size unit is normally assigned the task of constructing a 300-meter section of double-apron fence?

The construction of a 300-meter section of either a 4- and 2-pace or a 6- and 3-pace double-apron is normally assigned to a platoon.

12. Which wires (numbered in sequence of installation) form the backbone of a double-apron fence?

Wires numbers 6, 7, and 8 (rear apron) form the backbone of a double-apron fence. They hold the pickets in position.

13. What does wire No. 12 of a double-apron fence have in common with wire No. 2?

Both wire No. 2 and wire No. 12 are trip wires. Wire No. 2 is installed on the enemy side and wire No. 12 on the friendly side of a double-apron fence.

14. After the pickets for a triple concertina fence have been installed, where is the first roll of concertina placed by the personnel that lay out the wire?

The personnel that lay out the concertinas drop the first roll at the third picket in the front row. The other rolls are placed at every fourth picket from where the first roll was dropped.

15. Why is a strand of barbed wire stretched tightly along the top of front row concertina sections in the construction of a triple standard concertina fence?

A strand of barbed wire is stretched tightly along the top of front row concertina sections in the construction of a triple standard concertina fence to increase the resistance of the fence against crushing.

16. What barbed wire obstacle is used equally well in snow, rocky ground, or marshland?

The Lapland fence can be used equally as well on frozen or rocky ground and in snow, bogs, or marshlands. The wire is attached to tripods (fig 6-32) instead of pickets.

17. Which barbed wire obstacle is constructed about 23 centimeters above the ground?

Situation: Given perimeter defense:
Tactical wire mean perimeter = 800 meters
Protective wire mean perimeter = 600 meters
Supplementary wire mean perimeter = 1000 meters

Trip wires are stretched about 23 centimeters above the ground. The tanglefoot is constructed at heights varying from 23 to 75 centimeters. Spirals of loose wire are wound around a form of 1-meter posts on which the wire is extended from the bottom of the posts (above ground) to the top. A knife rest is approximately 1 meter high.

18. Estimate the amount of material, the truckloads, and the manhours required to construct one band (three belts in depth) of tactical wire using 4 and 2 pace double apron design. The fence will be constructed during daylight hours by inexperienced troops using U-shaped pickets and barbed tape.

Tactical Wire:
800 m mean perimeter x 1.25 3 belts = 3000 m effective length

19. Estimate the amount of material, the truckloads, and the manhours required to construct one belt of triple standard concertina for protective wire. The fence will be constructed during the daylight hours by experienced troops using U-shaped pickets and barbed wire.

Protective Wire:
600 m mean perimeter x 1.10 x 1 belt = 660 m effective length

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