Dead-point meaning

The position of the connected point of the crank-arm in question at such an instant is called a dead-point.

The velocity of the other connected point at such an instant is null, unless it also reaches a dead-point at the same instant, so that the line of connection is in the plane of the two axes of rotation, in which case the velocity ratio is indeterminate.

It takes minimal effort from the operator to move the handbrake lever past this dead point.