I agree with Jinx - there is unfortunately no reliable way to visually sex a BP - BUT if you don't have a vested interest in your snakes gender, then pick one!

Also - tape - bad idea! Imagine taking it off of yourself, ow.

Critter tank - If your tank is the one I think it is, there should be a small set of holes on the front, where you can lock it shut with a padlock. I have a few myself and I just slide a hook through the hole, its enough to keep the lid from sliding out - even the big snakes cant push it enough to bend/break whatever you put in that hole.