Anyone have a poor man's way of doing vertical knee raises?
 

I'm not ready to drop $200 on a captain's chair, but I'm past being able to comfortably do knee raises with my arms on the dip handles of my rack. I have a full cage, and I know I used to see straps that hook to the chin-up bar and then under your elbows, but I'll be damned if I can find them and I never liked them that much anyway, no control over your back.

I know there are some fitness buffs here, so wow me. :)

that is really stupid how one of those so expensive you could take some pipes and put them between saw horses but i dunno you probably can really work the parts without property grip the straps you are talking about can ususally be rigged if you have two back support belts (the ones you use for squats.