what do you want Richard?? More pictures? a diagram? a complete history of all the people who raise baby snakes in shoe box size poly totes??

use a modest wattage bulb, 30-40 watts will gently warm one end.

Flexiwatt - A very well known heat tape product could also be placed underneath one end to provide a nice little hot spot.

Garter snakes are not rocket science, they thrive outside in conditions far inferior to the inside of that cage.