Wood Knot

Interlocking Puzzles,
circa 2000.

(3 wood pieces, 2.75")

Daniel C. Alsmeyer 2006,
Sabriday Puzzles.

(3 wood pieces, 3")

"Triple Cross",
Puzzles & BT 2006.

(3 wood pieces, 3.2")

Three examples of the wood knot that was patented by M. P. Rao in 1980. Here are the directions that were sold with the Sabriday version:

Further reading:
Rao Patent, from: www.uspto.gov - patent no. 4,198,053