The mattresses should be backed with joiner doors, steel plates, or wooden plates made of cleated planks, and they must
be shored stoutly in place. Holes or cracks into which the mattress cannot be pushed may be stuffed with rags, oakum,
and wedges. In some cases, these patches have not been satisfactory but they have given good results over many shell
holes and in replacing damaged watertight doors.
h. Pillows, blankets, and kapok life jackets. Feather pillows do not make effective patches or gaskets over a long
period of time. When the feathers get wet, they will collect in a lump at one end of the ticking cover, and the patch
practically collapses. Furthermore, if the casing rips, the feathers come out and clog the pump strainers badly. Kapok
life jackets are more effective. Folded blankets can be used in place of pillows.
i. Box patch. A suitable patch for use over holes having jagged edges protruding inward is a steel box running in
sizes up to 18 inches square and 6 inches deep. The box is open at one end and has a gasket running along the facing
edges. The gaskets may be made of rubber or of canvas stuffed with oakum. The box is put over a shell hole from
inside the ship and is held in place with shoring. When the compartment is pumped dry, the box may be secured by
welding angle clips between the box and the hull plating, after which the timbers can be removed for use elsewhere. The
box cannot readily be fitted to uneven surfaces, so variations have to be made in its use. One variation is to stuff the
box with pillows, or to lay pillows over the hole before applying the box. This has proven successful. Another variation is
to stuff rags and wedges into holes between the box and the rumpled hull. In the absence of ready-made steel boxes,
similar patches can be made of planks. The advantage of a wooden box is that its edges can be shaped with a hatchet
to fit closer to corrugations in plating. It is suggested that large ships make and carry box patches in sizes up to 4 feet
square and 1 foot deep.
j. Bucket patch. An ordinary galvanized bucket can be used in a variety of ways to stop leaks. It can be pushed
into a hole, bottom first, to form a metal plug, or it can be stuffed with rags and put over a hole like the box patch
previously described. It can be held in place by shoring or by using a hook bolt which will be described later.
k. Hook bolts. A hook bolt is a long bolt having the head end so shaped that the bolt can be hooked to plating
through which it has been inserted. The common types are the T, the J and the L, as illustrated in FIGURE 8-1, so called
because they resemble those letters. The long shanks are threaded and provided with nuts and washers. Steel or
wooden strongbacks are used with them, generally the latter. The bolt has no regular head.