'To frap' is a fairly archaic term meaning to bind or tie together tightly. The terms 'frapping' and 'frap' are still used in shipping. However, the noun 'frap' has it's greatest modern use in scouting.
Scouts are still taught the fine art of lashing -- binding together spars to make simple structures. These lashings consist of 'wraps' and 'fraps'. A wrap is a turn of cord made around spars, while a frap is a turn made around the rope itself, to help bind it more tightly. Generally, one fraps a rope by maintaining strong tension on the cord while turning it around the lashing twice, usually securing it with a simple clove hitch or square knot.
Scouts use 'frap' and 'frapping' as a noun and a verb; however, it seems to be most common to use them both as nouns: 'tie the frap', 'secure the frapping'.