Scotch Indoor Mounting Tape, Holds up to 6 pounds, 1×1 inch, 48 squares – Link
Amazon has this marked down to $2.97.
- Double-coated 1-inch foam squares
- Adhere and conform to a variety of surfaces
- Ideal for mounting pictures and decorations on most types of walls
- Permanently bonds to most surfaces
- Squares hold up to 2 pounds