A step wedge is a device of layered metal steps of varying thickness used to:

a. determine film freshness.
b. determine safety of the safe light.
c. evaluate tube head stability.
d. test the strength of processing chemicals.

d. When using a step wedge, several films are exposed at the same settings, all at the same time. One of these films becomes the reference film, the one that the remaining films are compared to for the purpose of monitoring the strength of the processing solutions.