We had the same problem, we couldn't figure out how to mount the bar so that it would hold without screws. It didn't even hold our kids of 30 kg. Unfortunately, we couldn't return it either, as it wasn't worth it at this price. We think it was an absolute mistake.

If by "rubber grips" you mean the foam tubes at the grip positions: These "tubes" are not glued, but they fit very tightly and don't slip, so I can't imagine that they can really be removed from the bar without damage.

Hi Martin I have already tested the pull-up bar between wooden door frames. This works. However, the door frame should be very stable and not bend. Since this is not the case at home, I use the bar in the basement between the concrete door frame. It also comes with two brackets that are the best way to hang the rod for permanent attachment. - This seems pretty good - but I haven't tested it yet. I am very happy with the rod! 👍🏻