24. 6. 2015 v 12:53, Erin Lynch <hongmeiguicc@yahoo.com>:

We use a colour laser printer, cut out each protractor, and then "laminate" them individually by covering them several layers of clear sticky tape. The tape needs to be wider than the protractor, so you can place the protractor on the tape and then fold the tape over along the ruler-edge side of the protractor. This gives you a nice smooth ruler-edge for drawing your centreline. 


It is probably better to use good inkjet and special transparent material. Inkjet is able to make thinner lines. And you may buy special transparent cold laminating tape.

For example:

http://solutions.3m.com/wps/portal/3M/en_US/Adhesives/Tapes/Products/~/3M-Scotchgard-Multi-Layer-Protective-Film?N=5003212+7574546&rt=r3
http://www.surfacearmor.com/applications/glass-surfaces/

Just ask for free samples :)

m.