FIGURE 8-1. Types of Hook Bolts.
l. The head end of the bolt is inserted through a hole and the bolt is rotated or adjusted until it cannot be pulled
back through the hole. A pad or gasket, backed by a plank or a strongback, is then slid over the bolt, and the patch is
secured in place by taking up on the nut. Generally it is necessary to use these bolts in pairs. Hook bolts can be used in
combination with many of the patches previously mentioned, especially the folding plate, the box, and the bucket.
m. Folding T. A variation of the hook bolt is the folding T. It resembles the T-bolt, but it has a hinge where the
shank joins the crosspiece so it is much like the tumble toggle bolt. This bolt may be folded and inserted through a small
hole; when pulled back, the crosspiece catches on the hull plating. By using this bolt, a crew member standing inside the
ship can put on a patch either inside or outside the ship. By means of retaining line on the bolt, a strongback and a pillow
can be threaded over the line and the entire patch folded and tossed out through the hole. When the line is hauled in,
the patch takes up against the ship where it can be readjusted to give a tighter fit; or the pillow and plate can be pushed
over the shank inside the ship, which will give an inside patch. Nuts and washers are provided for holding and tightening
the patch. It might be well to put large wings on the nuts.