A
fish tape refers to a
long,
flat,
skinny, and
flexible piece of
steel wire used by an
electrician. These devices are very useful for running through sections of electrical
conduit for the purposes of
pulling wire through the pipe, or to pull other things such as
rope through the pipe.
Fish tapes work because they are bendy enough to easily go around corners and curves in the pipe, but strong enough to be pushed through the pipe without folding on itself and capable of pulling other items back through the pipe without breaking.