The crank axle has tapered square ends, the crank arms have mating tapered square ends. The crank arm is pressed on and the taper ensures a snug fit. A special tool is required to remove a cotterless crank. Crank Axle The axle about which the crank arms and pedals revolve. Looked down upon by tweak cyclists, but used widely in the Pacific Northwest and many non-US parts of the world.
Helps keep the rider cleaner and drier.
It also has places to attach accurate measuring instruments like dial gauges, scratch needles, etc. High-Wheeler A bicycle with one large wheel and one small wheel. Rooster Tail A spray of water flung off the back wheel as the bicycle rolls through water. Particularly pronounced on bikes without fenders.