Hard proof is a digital printing sample that is ideal to check colors.
A hard proof is mainly meant to check the color, and not the final product paper or binding, as it is printed a digital Epson printer and not with an offset printer. What helps hard proof get a color sample as close as 95% to the final products color is the GMG color system that helps control the color. A hard proof will be a set of page by page color printing proof that will not be bound like the final product. So, for clients who need to check the paper and binding quality, it is recommended that they use a dummy.