Inside every prayer wheel is a tightly wound paper scroll printed, traditionally by woodblock, with a mantra, commonly Om Mani Padme Hum, repeated many thousands of times on a single long strip, and producing that scroll is a specialist printer's job entirely separate from building the wheel that will hold it.
Two different crafts joined in one object
The drum itself, whether a small handheld cylinder with a weighted chain that helps it spin, or a large fixed wheel set into a monastery wall, or a water or wind driven wheel that turns on its own, is metalwork, commonly copper, brass or silver, made by artisans who may never print a scroll in their lives. The two trades meet only when the finished scroll is sealed inside the finished drum, and a wheel with a torn or damaged scroll is opened and refitted with a fresh one rather than discarded whole.
Who may spin it, and the one binding rule
Anyone, ordained or lay, Buddhist or simply curious, may spin a prayer wheel, there is no initiation requirement, but the wheel must always be turned clockwise, the same direction the mantra inside is understood to be read, and turning one the wrong way is considered to work against its purpose rather than simply being a harmless variation.