The earliest Model T’s did not come equipped with a starter, so the hand crank was or is the only way to start the engine other than push starting. The fellow above is displaying risky form. You should never wrap a thumb around the crank while cranking, and all pressure on the crank must be upwards.
The crank bushing wears out from constant use. Very seldom did anyone bother to lube the crank bushings. And with the bushing on the front of the car, mostly exposed to the elements, water gets in and causes rust. At some point the Model T mechanic will need to replace a crank bushing for one or all of these reasons. Let’s take a look at how it is done.