Set of 3 Half-hitch tools Black. Slender metal cylinders with holes at the end the allow you to tie in a quick half-hitch to hold the thread when in the middle of tying a fly. To use the tool you first match the size of the hole in the end of one of the tools to the size of the hook eye and then lay the tool on top of the thread, twist the thread around the tool once, and with the tool up against the eye, slide the thread off onto the hook to make the half-hitch.