Just wanted to share that I was able to VERY satisfactorily repair an old tail light lens for my 79! A corner of the clear lens had a crack that went all the way through. I didn't know until I disassembled them for cleaning. Well, I cleaned the lens and the edges of the cracked parts thoroughly, and then I was able to "plastic weld" the broken piece back on with a cheap soldering iron. I didnt add any new plastic, I just held the broken piece in place, then kind of traced along the crack. This melted the two pieces back together. It's very strong too, I can support the whole weight of the lens by holding onto the repaired part. I did the plastic weld on the inside of the lens, the outside just looks like a faint crack.