A Watch-tackle or Tail-tackle is a luff-tackle purchase, with a hook in the end of the single block, and a tail to the upper end of the double block.
A Single Burton is composed of two single blocks, with a hook in the bight of the running part. Reeve the end of rope through the upper block, and make it fast to the strap of the fly-block. Then make fast your hook to the bight of the rope, and reeve the other end through the fly-block for a fall. The hook is made fast by passing the bight of the rope through the eye of the hook and over the whole. This is a very quick-working tackle and a strong purchase. Used for hoisting entirely.
When a very heavy weight is to be raised, the standing part should be attached to the slings by a fisherman's bend instead of to the block.
The size of blocks is expressed by the length of the shell in inches.
Tackles are also designated by the number of sheaves employed, as twofold (two single blocks), threefold (double and single block), etc.
The bight of a hook is the middle of the bend of the hook part.
Rope should always be stopped up, either with the end or with rope-yarn stops, to prevent its getting into a snarl. When using ropes for hauling, they should never be dragged upon the ground.
Before reeving a rope in a block the turn should be carefully taken out, to prevent twisting when the weight is lifted. This is done by stretching the rope out to its full length, and turning it in the opposite direction to that in which it is laid up until all the stiffness disappears.
Blocks should be overhauled very often to see that the sheaves are working properly on the pins, and that they work smoothly. If they do not, turn the pins end for end and rub a little black lead (graphite) on them to lubricate them; also on the sides of the sheaves where they rub against the shell.