Knex Trigger Help

hey instructables knex buiders,
i am aiming to make realistic knex guns that work but i don't understand how to make a trigger and put it in the gun. If you guys could send some ideas, I would be very greatful.

p.s. i am also taking knex gun ideas
p.p.s i will need a link to a picture for the gun
 thank you,
Jstahl414 

Step 1: My Gun Ideas

here are some of the guns i wanted to make