h, which
are filled in behind with sand. Always dig to full depth before
beginning to revet, as it is impossible to dig deeper afterwards
without loosening the revetting.

Revettments.--Every trench at points needs support, and this
_revetting_ may be done with any of the following materials: Sod;
corduroy of logs laid lengthwise; sand bags (size 20 in. x 10 in. x 5
in.); galvanized iron; chicken wire and cloth made in a frame about
six feet long; _hurdles_, wicker mats made by driving three-inch
stakes into the ground, leaving uprights as high above the ground as
the depth of the trench, then weaving withes and slender saplings
between the uprights; expanded metal; _gabions_, cylindrical baskets
made like hurdles except that the stakes are driven in a circle;
_fascines_, bundles of faggots about 10 inches in diameter by 9 feet
long. The faggots are laid together on a horse or between stakes
driven in the ground, then "choked," or bound tightly together, by a
rope 3 feet 8 inches long with loops at each end, tightened with two
stiff levers. The bundle is then bound with wire at intervals of two
feet. The circumference of a fascine should be 25 inches.

[Illustration: Plate #17]

Capt. Powell of the C.E.F. found during 18 months' service in the
trenches, that a separate construction for the bottom and firing step
from that of the parapet made repair much simpler when the trench was
damaged by shell fire. The upper part of the trench usually suffers
most, while the bottom section, if unattached, often remains intact
and the drainage system needs only to be cleared out. If the portion
above the firing step is one piece with that below, however, the whole
trench has to be reconstructed.

There is nothing more important than the supports used to keep
revetting in place. With sods, sand bags, concrete and gabions, a
proper arrangement in the first place will make other support
unnecessary.

Sod should be placed carefully, with a slope of not more than one
inch on four, with the vegetation uppermost. This type is least
affected by rain.

Sand Bags should be used like brickwork, laid in alternate headers
(binders) and stretchers. Their use should be confined as far as
possible to emergency and repair work, because after a few weeks the
bags rot and cannot be moved about. If the trench wall has been
demolished by artillery fire, the particles of cloth make digging out
the bottom of the trench a very difficult matt