Screw Gears are four gears with missing teeth, mounted onto screws. Screws A and C are righthanded, B and D are lefthanded. The goal is to screw the four screw gears into the frame, such that they line up. That is, the letters ABCD are straight, and each screw is all-the-way in. The challenge is in the missing teeth. Each gear has some teeth missing, and a blocking surface instead. Teeth of neighboring gears cannot pass these blocking surfaces. To solve the pieces, one needs to turn the screw gears sometimes simultaneously, and sometimes separately. Because of the missing teeth, not all gears go down at the same speed. This means that one should enter and turn the screw gears in a particular order.
Deisgned by Oskar van Deventer, who has created many different puzzles including his brand of Oskar Puzzles which are mechanical puzzles and objects that can only exist thanks to 3D printing technology. Since 1978, he has been creating hundreds of mechanical puzzles, making him one of the world's most prolific designers. Several of his innovative designs are commercially available.