This is a self enclosed team marker system that FTC team 13712 used on our robot this year. X-Bots is our name btw, hit us up with your 3d printing questions. This self contained unit is designed for the goBuilda 2000 series dual mode servo, and an actobotics .77" aluminum servo horn. It works very reliably although low print speeds are required for it to work properly as the teeth are quite small. It has worked 100% of the time. If you would like to reuse our marker design, although quite simple, you just need to make a box with a hole that has a similar shape to the angled end of the rack, and it will hold on when you want it to and deploy easily when you don't. It was intended to be attached to a 3" piece of actobotics pattern bracket, with a piece of x-rail attached to the middle, although a few minor mods can make it easily suit your needs. Print the block with supports!!!!!! make sure your rack and pinion layer heights match and your block layer height matches the rack. Finally remember you gracious professionalism and HAVE FUN!!!!!!
p.s. a 3 inch pattern plate can also be used to cover the open side of the block to keep wandering fingers out of the mechanism as 1 it is delicate and 2 it hurts when you get your fingers caught in it... I unfortunately can speak from personal experience