This section is from the book "Modern Buildings, Their Planning, Construction And Equipment Vol6", by G. A. T. Middleton. Also available from Amazon: Modern Buildings.
When a load of any kind has to be raised by means of the gin wheel or blocks and fall it usually has to be attached to the lower hook of the lifting implement by some means other than its own handle, except in the case of a bucket. For this purpose sling chains, made in various lengths and provided with convenient hooks and rings, must be provided. One of the most frequently used sling chains consists of a piece of chain about 5 feet long, the links being made of 3/8 diameter iron, having a ring in the centre large enough to pass easily over the hook of the blocks or crane, and a small hook at each end. These latter can be passed through the handles of a skip or basket for raising bricks, or taken round almost any piece of stone or timber and hooked back into the centre ring, making a sort of cradle in which it can be safely lifted (A, Fig. 214). Another useful arrangement of the sling chain is that by which an ordinary navvy barrow and its load can be attached to the blocks and lifted, maintaining its horizontal position throughout the entire operation (B, Fig. 214). This is achieved by having three lengths of chain dependent from the centre ring, two of which are the same length (about 4 feet) and the third somewhat shorter (3 feet). The two longer chains each have a ring at their free ends large enough to slip easily over the handles of the barrow. The shorter chain is supplied with a small hook, which can be passed under the rim of the wheel.
A good supply of straight pieces of chain provided with a hook at one end and a large ring at the other, of varying length and thickness, will also be found among the necessary plant when the building in hand has reached any considerable height.