I use a loop of boot lace and hang it over BOTH door knobs.
A loop on one knob only will pull that knob off... I have to strop
with an open door but it works.
One additional thing to watch for is how well anchored the
hook is. You want to get a solid connection... dry wall
and plaster will not hold up. The handy man in the group will
find a plank of hardwood and finish the edges and bolt it to
the wall at the studs. With time there will be scratches and
wear but with a 'plank' in place the wear will look planned and
purposeful.