5. Nos. 2 and 4 drive in their picks (half way between themselves and left-hand neighbors and in line with their toes). 6. Front rank to mark out tasks (Nos. 2 and 3 commence from the pick between them and mark out 7½ feet each way, that is, 2½ pick-handles’ distance). 7. Rear rank mark out tasks (commencing from pick between Nos. 1 and 4 to end of each recess). As soon as this is done the men commence work, the officer going down the line at once to check any errors before they have gone too far. While this may sound very complicated it will be found that after a little training the men become accustomed to it and it is a very simple matter. This method renders unnecessary the giving of many orders in the dark once the men are extended, and prevents a great amount of confusion. There will always be a slight amount of readjustment of the work, such as the widening of traverses, etc., but it is easily done after the work has been started and even after the trench has been dug to some depth. OBSTACLES AND ENTANGLEMENTS The purpose of an obstacle is to obtain the control of the enemies in respect to direction and speed during an attack, and to deflect troops into areas favorable to their destruction by the defenders. They break up the unity of action, deflect parties isolated into the best swept fields of fire and hold them under close fire of the defenses. An obstacle should be close to the defender’s position, not more than 80 yards away at the most. A system is now in use on the Western Front where entanglements in front of trenches are placed approximately 20 yards from the parapet, as that has been found to be the distance at which the deadliest bombing can be done. They should be sheltered or screened, when possible, from enemy artillery, giving no cover to the enemy and be so placed as to surprise the enemy. They should not interfere with any counter attack necessary to be made and have occasional gaps, which may be mined. Types of obstacles are low wire entanglements, their height depending on the condition existing in No Man’s Land; high wire entanglements, barricades, mines, inundations, etc. Wire plays the important part in most of the obstacles now being used on all fronts, and is generally used, first, as a trip wire stretched just above the ground, or fastened in loose coils to short pickets. Flares and alarm guns and tin cans may be used in connection with this; second: a simple fence to cause delay and confusion to the enemy at night; third: as a concealed obstacle in fords and standing crops or long grass; fourth: as a help towards making hedges and brushwood impassable, and as a wire entanglement solely. The wire entanglements are the best obstacles, as they are quickly and easily made, are very difficult to destroy and offer no obstruction to fire in view of the defenses.