At the sharp edge.

I love masking tape - couldn't paint without it. But it has to be the right brand - not the most expensive but the most reliable. Just a quick tear against my clothing before applying and it always comes off like a dream. Now you may be a gluer or a hair-drying masking tape kind of user - whatever it takes to get that lovely sharp edge - the thrill of the reveal which makes your artwork really finished. My absolute favourite is the one with 'WET PAINT' printed on and I often keep it when it's peeled off, covered in wonderful colours, and collect it in my sketch book. Odd? Not really. I saw someone on TV last week who kept their nail clippings in a jar so it's really not even worth a mention.