Ray,

A slinky is a length of tubing, often parachute cord, stuffed with weight of some sort (split shot, shotgun shot, ball bearings) sealed on both ends with a snap swivel on one end. Tie that to your line (I used tag end of surgeon's knot the fly was tied to) and it takes the rig down in a hurry - the design helps avoid snags.

Regards,
Scott