Steve wrote:
I have an up & over metal garage door that stays up when I open it
most
of the time. The problem is that every now and again it drops down
again, by anything from about 6 inches to 2 or 3 feet. This often
happens some time I have opened it and carried on, happily believing
it
has decided to stay open. It's already taken a lump out of the top
of
my head

Ouch. This reminded me of :

Also beware of your loft hatches, I had mine come down on my head as
(unbeknown to me) it had a faulty catch. Until this point I thought
seeing stars was just in the cartoons, along with the comedy head lump.

Cheers,

Paul.