Had an idea and need some help. :P I utilised my incredibly epicfail drawing skills to try and help explain this, as the part I need for the key part of my idea, I have no idea what they're called. :P
Basically: I reckon I can make the blade out of wood pretty easy, and a casing to attach to my arm via the guantlet pretty easy too. The bottom of the blade, the end that would be closest to my elbow while in the casing, would be thicker, which would stop it falling out of the casing. At the elbow end of the casing, I thought I could put in those little ball bearings that push in and out (this being what I don't know what to call :P), so that the thick bottom of the blade can push past them, and once it's past, they would hold the blade inside the casing. Then, with enough force from a downward swing of my arm, the thick bit could get past the bearing thingies, and slide out. Then, hopefully, with a forceful enough movement, the blade will slip back in and the thick bit will go back past the bearing thingies, locking it in place.
Tell me if that didn't make any sense - I get the feeling it didn't. At all. ^^;;; Anyway, here be a couple of shots of the little drawing I failed at to try and help explain what I mean:
Blurry and horrible, I know, I don't have a scanner. :P Opinions plz, and PLEASE, can someone tell me what those bloody ball bearing thingies are actually called so I can buy some? xD