Kerry: A half cab noseslide is when you're riding backwards facing a ledge. You're going to want to have your half cabs on lock and your noseslides on lock, to have those both solid tricks. You're going to be riding parallel, you're going to half cab, force all your weight up onto the nose of the board, and then you're going to be sliding ahead. Definitely have half cabs and noseslides on lock before you start doing these tricks.
Bam: If you want to do a switch, then it's an ollie tailslide, but it's all the same thing pretty much. Approach the ledge, ollie, then tailslide; or, same thing, half cab, noseslide. It all depends on which way you want to do it.
Kerry: All transferring your weight from the rear of the board to the front, and landing, then sliding. Make sure you wax it nicely, because it usually doesn't slide when you're first learning it.
Bam: That's your half cab noseslide.