WI winter temperatures dip way below zero, in fact students have indoor recess or come into the school building in the morning only when the temperature goes below -5 degrees. So if I want to hang artwork on an outside wall it's normal for the work to start falling off within a day because of the moisture that builds up on the inside warmer wall. The mallet is the trick that keeps the artwork up for weeks.
About 10 years ago I learned this trick. I was involved in a big artist-in-residence program at my school and we were using a lot of old, curled up paper hanging from masking tape on cinder block walls. If you whack the tape with the rubber mallet a couple of times the paper stayed put on the wall. We could take the paper down and rehang it with the same masking tape several times if we whacked it with a mallet every time we hung it. Since that time I have kept a rubber mallet in the desk drawers of both of my schools for the rather infrequent times I need it.
You need to remember to move your head to the side when you whack the mallet, there is a spring back action to it and you don't want your nose in line with it -ouch!
