Window lock

A basic window latch system widely used in Europe. Attach the mount to the wall beneath the window. Attach an arm (8, 11 or 14cm) to the mount and then the lock to the window. Slide the arm into the lock to keep the window from moving while opened.

Plastic shrinkage should not be a problem with this model since all pieces will shrink the same. It can be scaled up and down freely based on your needs (just make sure you scale each piece the same)