The thickness check is a tool for verifying wall thicknesses, especially useful if you are designing plastic and cast parts.
When you use this analysis tool, pro/e essentially cuts the part using a specified plane and creates a temporary x-section. When thickness falls in between the set range of min/max thickness values, the x-section appears as a normal yellow planar x-section.
Wherever the thickness of the section is greater than the maximum specified, the area(s) of the x-section are outlined in red. When the thickness is below the minium specified, the area(s) of the x-section are outlined in blue/cyan.