I have found that for short term, Velcro works, if the room or building is
not too hot, or the walls haven't been washed with an industrial cleaner. I
have begun using hot glue for longer term exhibitions. As Mark said, it's
quicker and does come off with a knife of sorts.
I sued to use tape for a month long show at Barnes and Nobles. I was putting
the pieces up each day. Finally used Velcro, which works there, but makes a
mess of their walls. They don't seem to mind. The walls of my school are
epoxy covered cement blocks or ceramic tile. The only thing that holds is hot
glue. In the Cafeteria we have to use hot glue. Everything else falls down.
But it damages the painted walls. The Principal is with us on this, thank
Hot glue was mentioned on this list last year. I have blessed the that day