material :
2 wooden plank of 10X15 cm (1)
2 wooden plank of 7x15cm. (2)
1 wooden plank of10x20 cm (3)
A laser
1 plank of Plexiglas of 10x18 cm (4)

Protocol :
Broke the laser to get the transparent lens and fix it in the hole made in the center of the plank 3
Make a slot on the top of each plank 1 to create a channel for a string
Hang the plank 4 with a string by each side of the plank thank to holes made on each corner
Stick 2 wooden planks 1 to the plank 3 with wood glue
Hand the Plexiglas plank to the structure by set up the string in the channel
Cut two slot on the plank 4 to make plank 2 cross it. Plank 2 will be columns
Fix all the structure on a wood base