Heel!

http://www.google.com/patents/about?id=BYQJAAAAEBAJ

How do you make a collar for a creature that’s all neck?

Standard animal collars such as designed for dogs and cats as well as other legged animals are not designed for the body style of a snake because the snake has no external appendages. … The concertina motion of a snake coupled with an ability to alter the shape of its circumference enables it to move through and escape any known annular restraint such as a neck-style collar.

Donald Boys’ snake collar, patented in 2002, includes a “concertina movement neutralization device” that prevents these escapes so you can take your snake outdoors. “A reptile getting more sunlight will have a better skin condition than one kept in the dark.”