Figure 6-9. - An inverted gun tackle.

A TWOFOLD PURCHASE tackle consists of two double blocks (fig. 6-11). It has a mechanical advantage of 4.

A DOUBLE-LUFF tackle consists of a triple block and a double block (fig. 6-12). It has a mechanical advantage of 5.

Figure 6-10. - A single-luff tackle.

Figure 6-11. - A twofold purchase.

Figure 6-12. - A double-luff tackle.