The terms used to describe the parts of a tackle
(fig. 6-3) and various assemblies of tackle are as
The block(s) in a tackle assembly change(s) the
direction of pull, provides mechanical advantage, or
The fall is either a wire rope or fiber line reeved
through a pair of blocks to form a tackle.
The hauling part of the fall leads from the block
upon which the power is exerted.
The fixed (or standing) block is the end which
is attached to a becket.
The movable (or running) block of a tackle is
the block attached to a fixed objector support. When a
tackle is being used, the movable block moves and the
fixed block remains stationary.
The frame (or shell), made of wood or metal,
houses the sheaves.
The sheave is a round, grooved wheel over
which the line runs. Usually the blocks have one, two,
three, or four sheaves. Some blocks have up to eleven
The cheeks are the solid sides of the frame or
The pin is a metal axle that the sheave turns on.
It runs from cheek to cheek through the middle of the
The becket is a metal loop formed at one or both
ends of a block; the standing part of the line is fastened
to the becket.
The straps inner and outer) hold the block
together and support the pin on which the sheaves
The shallow is the opening in the block through
which the line passes.
The breech is the part of the block opposite the
To overhaul means to lengthen a tackle by
pulling the two blocks apart.
To round in means to bring the blocks of a tackle
toward each other, usually without a load on the tackle
(opposite of overhaul).
The term two blocked means that both blocks
of a tackle are as close together as they can go. You may
also hear this term called block and block.
Blocks are constructed for use with fiber line or
wire rope. Wire rope blocks are heavily constructed
and have large sheaves with deep grooves. Fiber line
blocks are generally not as heavily constructed as wire
rope blocks and have smaller sheaves with shallow,
wide grooves. A large sheave is needed with wire rope
to prevent sharp bending. Since fiber line is more
flexible and pliable, it does not require a sheave as
large as the same size that wire rope requires,
According to the number of sheaves, blocks are
called SINGLE, DOUBLE, OR TRIPLE blocks.
Blocks are fitted with a number of attachments, such
as hooks, shackles, eyes, and rings. Figure 6-4 shows
Figure 6-3.Parts of a tackle.
Figure 6-4.Heavy-duty blocks.