Certain mountain bikes come equipped with a through axle. This type of bicycle axle is enclosed on all sides, providing a safe and effective interface between the wheel and the frame for off-road travel. Removing the rear or front wheel from the bicycle necessitates first removing the through axle from the wheel. Through axles use either a pinch bolt or quick-release skewer to secure the axle in place.
Use a 5mm Allen key and turn the pinch bolt counterclockwise at the end of the through axle, if so equipped, to loosen it.
Open the quick-release lever at the end of the skewer, if so equipped, and turn it counterclockwise to loosen the through axle.
Slide the loosened through axle off the rear wheel. The rear wheel can now be removed from the bicycle as needed.