File:US Navy 030327-N-1290G-003 Plane Captains take a relax and play some "hackey-sack", on the flight deck aboard the aircraft carrier USS Harry S. Truman.jpg - Wikimedia Commons
Sack AS-6 - Wikiwand
Sack Ups Plane Sack - Jack Plane SU546 - Classic Hand Tools Limited
Sack AS 6 | Plane-Encyclopedia
aviation history - Has anyone attempted to recreate the Sack AS-6 (German Saucer-wing)? - Aviation Stack Exchange
Plane Sacks - Lee Valley Tools
WoodRiver Smooth Plane Sack-Up - Hand Planes - Amazon.com