Spiral retaining rings from Smalley Steel Ring Co., Wheeling, Ill., give designers a new type of tamperproof fastener. Intended for use in inner-diameter/outer-diameter locks, the rings require no tools, can rotate 360, and they're hidden when installed.

In the illustrated application, the ring is first installed in the housing groove. When the mating component is added, the ring is pushed into the housing groove, which is deep enough to hold the ring's radial wall as the component slides past it into position. When the grooves meet, the rings snaps to its full size and into the shaft groove, making a sturdy connection.