Please do not use tape of any kind to try to trap the snake. Tape of any kind on a garter snake can cause serious injuries. We have had members lose snakes due to wounds from tape. Is there a way that you can leave some food and a water dish in the basement for the snake? Another trick to try is to warm some towels in the dryer and then leave them in a big pile for the snake...snakes will often go to the warm pile and burrow. Check the pile often.