In short, the thigh is a saw with two parallel edges, separated by a groove in which the foreleg lies when folded.
The foreleg, which is attached to the thigh by a very flexible articulation, is also a double-edged saw, but the teeth are smaller, more numerous, and closer than those of the thigh.

It terminates in a strong hook, the point of which is as sharp as the finest needle: a hook which is fluted underneath and has a double blade like a pruning-knife.
A weapon admirably adapted for piercing and tearing, this hook has sometimes left me with visible remembrances.

Caught in turn by the creature which I had just captured, and not having both hands free, I have often been obliged to get a second person to free me from my tenacious captive! To free oneself by violence without disengaging the firmly implanted talons would result in lacerations such as the thorns of a rosebush will produce.

None of our insects is so inconvenient to handle.

The Mantis digs its knife-blades into your flesh, pierces you with its needles, seizes you as in a vice, and renders self-defence almost impossible if, wishing to take your quarry alive, you refrain from crushing it out of existence.
When the Mantis is in repose its weapons are folded and pressed against the thorax, and are perfectly inoffensive in appearance.