Hint B3 - K'NEX Light-up bricks
The K'NEX light-up brick contains batteries and tiny lights.
The brick comes with 3 batteries already installed, as shown in the photo. Tap the light-up brick to make the lights start flashing.
To replace the batteries, remove the screw, and insert 3 button cell (LR41 or AG3), matching the +/- as shown.
Please also view important information about batteries.
To use the light-up brick in your model, attach transparent 1 x 1 bricks above the light holes at the top of the light-up brick, as shown in the photo.