2020 updates by Cathy Bickel
A coconut makes a snug, inexpensive and durable nest-box.
Purchase a large coconut without holes, cracks, or score-marks. Drill a hole in the end without an indentation and drain the milk. Cut or drill an opening large enough for gerbils to enter. Place the coconut in an oven set to 200°F for 2 hours or until the meat is dry.
Chip the meat out and wash with warm, soapy water. Let the coconut dry. If it retains an odor, fill it with baking soda and let it sit for several days, turning it daily. Empty the coconut shell and wash it again.