26

SEAMANSHIP AND NAUTICAL KNOWLEDGE

BLOCKS.

A built block consists of a shell, strop, sheave, pin, shackle or hook
The score of a block is the groove round the outside of the shell
(Fig. 71), to take the strop, rope, or wire, when one is to be fitted. The
cheeks are kept apart by two pieces of wood, one at the head and one at
the tail of the shell to form the "swallow," the name given to the space
the rope is rove through.

Fig. 71.
A Built Block.

Fig 72.

A Clump Block is cut
out of the solid wood.

Fig 73.

Sheave Plain Bush

The shells of blocks are usually made of elm or oak as both kinds
of wood are good for resisting weather but they must be kept varnished
or painted.

Fig, 74.—Sheave, Roller Bush,

Fsg. 75.—Metal Sheave,