I have a customer having trouble getting stickers to stick to these new fiberglass/plastic portable toilet doors. I told him "Sure, I'll show you how." I washed one with Dawn and water, rinsed it and dried it. Wiped it with alcohol. Pulled out a torch and flamed it. Put a sticker on and it felt good. Next day, corners are lifting and it's easy to peel. The stickers are supposed to stick, only I'm stuck.