These images originally appeared in a magazine called Bondage Life and you can find them elsewhere on the net

This first image describes how to tie the ever useful cinch noose. The cinch noose is a slip knot with a lot of friction. It "cinches up" easily but is difficult to loosen and nearly impossible to untie.

Combine the cinch noose with a wrist coil like this...

Insert your wrists into the wrist coil from opposite sides so that when you twist your hands palms together the coil will form a figure "8" around your wrists. Obviously you will have to position the cinch noose before getting both wrists into the coil. Note at first you may be tempted to make the wrist coil smaller than is necessary. You'll soon find even a loose coil tightens up nice and snug and struggling only makes it tighter. [1/4" inch (or greater) cotton line is recommended.]

This next image describes how to construct a special ring device which is useful for taking up the slack in a rope. It is often used as the centerpiece of bondage games where pulling a rope tight completes the bondage. Release usually requires obtaining a knife and cutting the bonds.