This lesson discusses the process of preparing the warp threads for setting up a loom, specifically the process of warping (in French, ourdissage). Warping is the operation that involves preparing the warp threads before they are mounted onto the loom for weaving tapestries. It details the steps for preparing the warp threads, creating the crenilles (groups of threads), using different wooden dowels for measuring and creating crosses (called encroix), and preparing the threads for installation on the loom.