Keyhole Cross

Three black shapes sit flat on a blue and yellow flat surface.
A red and yellow exhibit table with a blue, green and white information panel at the back, sit in front of two green and blue walls. On the table is a flat blue shape, with three black shapes on top.

Structures can be built using 'lock and key' shapes.

How it works

Three notched pieces of wood must be interlocked in sequence to create a three-dimensional cross.

Things to try or ask around the exhibit

Can you put the three-armed cross together?

Background

Some puzzle pieces can only be connected if they are interlocked before being pieced together.

Finding the science in your world

Locks have a jagged projection called a ward. Keys must have notches cut out so the key matches the ward. A second ward prevents anything but the right key from turning in the lock. Finally, the key engages the bolt to slide it back.