Closing scissor blade with trigger

This is an assembly that only requires a metal spring to operate. Place the spring between the compliant rack and the base.

Here is the link for the spring. It is the longer one in the set:

http://www.homedepot.com/p/Everbilt-1-4-in-x-1-1-2-in-and-11-32-in-x-1-7-8-in-Zinc-Plated-Extension-Spring-4-Pack-16086/202045462

Also check out this video of the thing working.

https://youtu.be/ok1IWjmO5H0

Best of luck!