There are 2 marbles enclosed in the puzzle on a curved base. The goal is to get the marble in each of the two holes on either end. As always, there is a trick.
Print base in a color
Lid should be transparent
Print or purchase 5/8" marbles
Number 4 x 7/16" long screws used (x4)
Modified designed based off Double Marble Puzzle by tomatoskins @ Instructables.