Here are some prototype tethers shared online by different people. Climbers have made stiff tethers out of cordage, stainless steel, aluminum, wood, and even plexiglas.
Eric Whipple, USA: http://www.treebuzz.com/forum/threads/oceans-tether-on-zz.24670/
Derrick Martin, USA: https://www.youtube.com/watch?v=aj_U4aqHCSo
Derrick Martin, USA: https://www.youtube.com/watch?v=7aWrmIFatgo
A history of stiff tethers from Derrick Martin, USA:
Mike Powers
Eric Whipple, USA: http://www.treebuzz.com/forum/threads/zigzag-and-rw-tether-my-avatar.31075/
Eric Whipple, USA: http://www.treebuzz.com/forum/threads/zigzag-and-rw-tether-my-avatar.31075/
Reon Rounds, USA: https://www.youtube.com/watch?v=u9pNKiH_g4g&t=55s
Reon Rounds, USA: https://www.instagram.com/reonrounds/?hl=en
Jack Burch: https://www.instagram.com/burchy2350/
Daigentanoen, Japan: http://www.treebuzz.com/forum/threads/compact-bulldog-bone.28246/page-217
Burrapeg, USA: http://www.treebuzz.com/forum/threads/final-really-ct-rollnlock-test-and-zig-zag-rope-wrench-thoughts.37425/
Daigentanoen, Japan: http://www.treebuzz.com/forum/threads/compact-bulldog-bone.28246/page-217
Mamoru Shimizu, Japan: https://www.facebook.com/photo.php?fbid=994132194068470&set=pcb.994132270735129&type=3&theater
Daigentanoen, Japan: https://www.youtube.com/watch?v=vEXKh5C8zYA
Daigentanoen, Japan: https://www.youtube.com/watch?v=QeJ67FqwigA
Someone in Poland: https://www.polskiarborysta.pl/zigzag-i-rope-wrench-czy-dozwolona-jest-taka-konfiguracja-n-42.html
From a conversation with Caleb Miller: https://www.instagram.com/piedmont.tree.climbing/
Patrick Brandt, USA
