The thickness of the profile is reduced towards the end of the sides. Saving paper and deceiving the customer are the aims of this practice. In addition, the round corner is also quite noticeable. This saves a couple of % in paper width.
A good quality edge protector consists of different layers of paper (greyboard) that are glued together. These layers of grey cardboard are wrapped in a so-called envelope (coverply) made out of testliner or krafliner. In addition, a good quality edge protector has a sharp angle that can withstand a pressure load.
Moreover, the edge protector consists of equal strips of paper with the same width (94 mm for a 50/50 profile) and a constant thickness over the entire width with a a maximum tolerance of 10%. The edge protector 50/50/3 is a commonly used profile nowadays but often with a less good finish
the width of the profiles (C and B) is measured with a calliper. The profile’s width also depends on the profile’s thickness. The length (A) can be measured with a conventional tape measure.
The thickness (D) is best measured with a feeler gauge for paper or a conventional calliper. Make sure not to measure at the edge of the profile when using a calliper as this is often a slightly thicker part due to cutting. Also check whether there is a difference in thickness in the sides of the profile. If the manufacturer uses different widths of paper for the protector, as shown in the picture above, this will be noticeable and easy to measure.