I designed this so I could make electrical connections with a needle. Just twist the knob to move the tip up and down. Meant to be used in conjunction with my tiny linear sled:

http://www.thingiverse.com/thing:603046

For this guy you will need 2-56 screws and nuts. Slide two nuts behind the stack so that the screws can go through. You can either push the twist knob onto the 2-56 bolt or glue it. A spring on the back side allows for smooth up and down motion.