When you pull back the front part hits the back edge of the square hole preventing you from over pulling the release tab. (humblemechanic.com)
The visually charged edges of the squares reveal glimpses of the individual colours in their pure form, giving the viewer an understanding of how the layers interact to create the finished work. (skny.com)
Gently but firmly press the rolling pin against the top and bottom edges of the square (this will help keep it square). (healthygreenkitchen.com)