Flat sheet metal becomes much stiffer after a flange, lip or channel is formed. This is why trolley shelves, book cart trays, drawer bodies, platform edges and side guards often use formed edges instead of simply increasing material thickness. Better bending design can reduce weight while keeping strength where the product needs it.
DoingMetal public content describes CNC bending with high accuracy and repeatability and states an allowable range of 0.5-20 mm depending on material. In practice, every bending job should be checked for part length, flange height, inside radius, tooling availability, material springback and whether holes or slots are too close to the bend line.
For trolley buyers, bending quality affects shelf fit, drawer movement, visible lines, edge safety, final width and how easily welded or bolted assemblies go together. It also affects packing, because knock-down trolleys often use formed panels and brackets that must assemble without forcing.