Yeah, the "Quad" was advocated by John Long for belaying off bolts, though I'm not convinced that it's worthwhile carrying a piece of equipment whose only purpose is for belaying off bolts. It consisted of a dyneema sling or tied loop, folded in half, and then having permanent limiter knots tied in it, such that there are four strands between the limiter knots. You'd then clip in to two or three of these strands.
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