And for those who do know ASCII off the top of their head, it's actually PETSCII. 205 (0xcd) is a right diagonal and 206 (0xce) is a left diagonal.

ASCII / (0x2f) and \ (0x5c) has three problems:

1. They're not as conveniently located (chr$(47+(rnd(1)*45) isn't quite as pretty)

2. They don't fill up character cell so there are gaps in the "maze"

3. PETSCII doesn't have a \ (0x5c is £)