Crease fix Minimum Fusing Temperature (MFT) is a measurement used to determine the performance and energy efficiency of a particular toner in combination with a specific paper type and a specific fuser (which fixes the toner on the paper). Crease fix MFT is measured by folding the paper across a solid fill area of an image and then rolling a defined mass across the folded area.

По сути и все.
Насколько понимаю, это - минимальная температура плавления при закреплении, к чему здесь "crease" относится?

Про crease area:
Optical comparison of the crease area is then made to a reference chart which provides a definition of an acceptable level of toner adhesion; alternatively, the crease area may be quantified by computer image analysis.