Chinning bars ruin door frames...

[flip.the.nuts]

I'm talking about the chinning bars you don't screw into your door frame, the ones that are portable. I really want to use one at my university accomodation, but they will ruin the door frame slowly, and of course I don't want to pay for a new door frame for them, lol.

Anyone got any ideas about how to prevent damage to the door frame?

Just trying to exercise

 

[comperic2003]

 

[tonynyc]

 

[flip.the.nuts]