At the office we have a bolt action biometric access device, and the door is never perfectly aligned, so the door bounces and the bolt doesn't align with the slot, and the door doesn't close. So I had to find a magnet strong enough to keep the door from bouncing yet not strong enough to keep the door from opening. I found an old 3.3" Platter Hard Drive and harvested the magnets from it, the strength was perfect and I designed the object to fit the magnets snugly.

Now the door works perfectly.