I have a spare Powerbar for sale after I got sent 2. It is a unit that fits into standard doorways without any screws at all, so that you can do pull ups/chin ups. What's great about it is that the bar is higher than the doorway, so even tall people can use it (not that I have that problem myself!)
It folds away flat, is very very secure and strong, and most importantly - easy to use.
Can hold up to 20 stone, won't damage or mark the doorway, and can be used on the floor for push-ups too (although how this is better than just doing push-ups on the floor I'm not sure!)
Dimensions: - 90cm (for use on doorway openings 685 - 785mm) - This is a standard door width as far as I know, and I've certainly had no problems with fitting. Best measure your door just in case!
Take a look at the official site for more details : - http://www.powertrainer.co.uk
Excellent product, not seen a bad review for it yet - I just don't need 2 of them!
I'd like £23 for it, collection only from TW11 (as it is quite heavy to post)
Collection only please from TW11