פירוש על כלים 24:8

של זגגים (frame of the glass-makers used to put their wares on) – they place upon it glass vessels.

There are three different types of beds:
One that is used for lying upon is susceptible to midras uncleanness; A regular bed made to lie upon is susceptible to midras uncleanness.

סרגין (frame of the netmakers) – those who make harnesses/riding seats. In Arabic they call מרכב/riding seat a SIREG. And there are those who interpret/explain that they strap (in zig-zag)/girth the lattice-work/mesh, and it is pure from everything, because it is not from what a person uses.

One used by glass makers is susceptible to corpse uncleanness; Glass makers would use the bed to arrange the glass that they had already made. This type of bed is considered a vessel and therefore is susceptible to impurity. I should note that some of the commentators ask why this type of bed is considered to be a vessel and is susceptible, whereas the wagon used in olive making (mishnah five) is pure. The same question might be asked concerning the next section: why is this bed susceptible but a bed used by weavers not?

And one used by weavers is free from all uncleanness. The bed used by weavers (there are various interpretations as to how this bed is used) is pure because it is not considered to be something used by a person.