My local film lab will no longer mount my 35mm slides, so I decided to get some equipment to do it myself. I bought the Seary Junior Mounting press, but I am not sure how to use it. The unit has a cast heating element which is pushed against the back of the unit by a knob. It looks like tightening the knob against the slide will heat the mount, and their is a curved piece below that which looks like it is intended to return the slide. I can't figure out how to position the slide in place, and hold it while tightening the element. I don't think my fingers should be near the heater. Also if I just loosen the pressure, what is to prevent the film from coming in contact with the heater? The unit came in the original box but with no instructions. Is there another part that is missing?