Keilim 20:6-7

Keilim 20:6

If one took a sheet that was susceptible to midras impurity and turned it into a curtain, it becomes insusceptible to midras impurity but it is remains susceptible to corpse impurity. Beis Shammai say that the sheet becomes insusceptible to midras when loops are attached to it; Beis Hillel say when loops are tied; Rabbi Akiva says when it has been affixed to the doorway.

Keilim 20:7

A mat made of reeds stretched lengthwise is insusceptible to impurity, though the Sages say it is susceptible if the reeds lay in the shape of an X. If they were laid across the width and there’s less than four handbreadths (about a foot) between reeds, it is insusceptible to impurity. If the mat was divided along its width, Rabbi Yehuda declares it insusceptible to impurity. Similarly, if one untied the knots on the ends, it is insusceptible to impurity. If the mat was divided along its length but three knots remain on the ends within six handbreadths (about 18”), it remains susceptible to impurity. A mat becomes susceptible to impurity when its ends are trimmed, which is the end of its manufacturing.