looking for input....

Degsy showed me this cool wheel chock thing in his truck... i am interested in making one for my fiddy so i can secure it in the bed of my truck... quicker and with less effort and less space req'd than the ten minutes it takes to tie it down and have it be a "quick release" kind of thing so i can take it out of the bed easily as well.

i have steel in mind for material... i need details on how those things work.. key fulcrum points or whatever it is that makes em do their job so i can try to make a mini-one?

Degsy? anyone?