To perform CBT safely, there are certain rules.

One must not leave a cock ring on or keep balls tied up for more than twenty minutes at a time or the lack of blood flow can cause the tissue to become necrotic (to die), or could cause permanent vascular damage.

"Do not break one's toys. Do not try to bend an erect penis over backwards or sideways, you can 'break' it.

Limit impact to a stiff penis the spongiform tissue is like a bunch of little blood balloons.

And be careful of what toys and tools you play with, especially when inserting anything into the urethra. You must sterilize tools before using them inside the urethra, and rubbing alcohol is not acceptable. Tools should be cleansed in a solution of diluted bleach to be truly sterilized.