Reference for Kelim 24:12

שְׁלֹשָׁה עוֹרוֹת הֵן. הֶעָשׂוּי לְשָׁטִיחַ, טָמֵא מִדְרָס. לְתַכְרִיךְ הַכֵּלִים, טָמֵא טְמֵא מֵת. וְשֶׁל רְצוּעוֹת וְשֶׁל סַנְדָּלִים, טְהוֹרָה מִכְּלוּם:

There are three types of hides: one made to be a rug is susceptible to <i>midras</i> impurity; [one made] to be a wrapping for vessels is susceptible to corpse impurity; and that which is to be [cut into strips and] used for straps or for sandals is pure from all [types of impurities].

Jastrow