Highlighter
grabcad
Was looking around the house for something to model up, this is what I came up with. If you drive the constraint in the assembly you can make the cap move in and out.
Download Model from grabcad
With this file you will be able to print Highlighter with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on Highlighter.