Book cradle
Mechanical book cradles that are designed for a support angle of up to 180° usually also have a so-called book cradle lock. This works like a brake that prevents the book cradle from making compensating movements during the scan and thus prevents blurring. In addition, there is often also the option of locking the book cradle as a whole by hand or foot switch and using it only as a flat support table.
Glass plate
Professional scanning systems that work with glass printing also have the option of locking the open glass plate to enable scanning without glass printing for particularly sensitive originals.