As @Eagle94-A1 said, adults can wear square knots on their uniform for certain ranks and awards that they earned as a youth: Eagle Scout rank, Arrow of Light rank, Venturing Summit Award, Quartermaster Award, religious awards, etc. There is a pretty good list here:
Awards or ranks?
Ranks, whether the patch or pin, are for youth and not to be worn as adults. Now some youth ranks: Eagle Scout, Sea Scout Quartermaster, Cub Scout Arrow of Light, Venturing Silver/Summit, and some discontinued older Explorer ranks, do have knots that represent the rank that adults do wear on their uniforms. And for Eagle, Quartermaster, Silver/Summit, and the older awards with medals, those are worn on special occasions.
As to awards, I do have some of the awards on uniforms because i can still wear them. But most of them ar eframed on wall.
Jeep's 8 Scouter Rules....1) It's a Scout led program. 2) Never do anything a Scout can do for themselves. 3) The Troop Leader is the Senior Patrol Leader. 4) The Patrol Method works ! 5) It is a game with a purpose. 6) Fail to plan and you plan to fail. 7) A Scout is Taught, Tested, Reviewed and Recognized. 8. The trail to Eagle is a trail, not a destination….