Nedarim 56B

מידי דהוה אמטה המיוחדת לכלים, דתניא: אם היתה מטה המיוחדת לכלים ⁠— אין צריך לכפותה.

this is just as it is with regard to the case of a bed designated exclusively for vessels, as it is taught in a baraita: If the bed in a mourner’s house was a bed designated for vessels and not for sleeping, one need not overturn it. The same is true with regard to the bed of fortune. Since it is not for sleeping, one need not overturn it.

אלא אי קשיא ⁠— הא קשיא, דתניא, רבן שמעון בן גמליאל אומר: דרגש ⁠— מתיר קרביטיו והוא נופל מאליו. ואי דרגש ערסא דגדא הוא, קרביטין מי אית ליה? כי אתא רבין, אמר: שאילתיה לההוא מרבנן ורב תחליפא בר מערבא שמיה, דהוה שכיח בשוקא דצלעי, ואמר לי: מאי דרגש ⁠— ערסא דצלא.

Rather, if defining a dargash as a bed of fortune is difficult, this is difficult, as it is taught in a baraita that Rabban Shimon ben Gamliel says: A mourner need not overturn a dargash; rather, he loosens the loops that connect the straps that support the bedding to the bedframe, and it collapses on its own. And if a dargash is a bed of fortune, does it have loops [karvitin]? When Ravin came from Eretz Yisrael to Babylonia, he said: I asked one of the rabbis about the meaning of dargash, and Rav Taḥalifa, from the West, was his name, who frequented the tanners’ market. And he said to me: What is a dargash? It is a leather bed.

איתמר, איזהו מטה ואיזהו דרגש? אמר רבי ירמיה: מטה ⁠— מסרגין אותה על גבה, דרגש ⁠— מסרגין אותו מגופו. מיתיבי: כלי עץ מאימתי מקבלין טומאה? המטה והעריסה ⁠— משישופם בעור הדג. ואי מטה מסתרגת על גבה, למה לי שיפת עור הדג?

It was stated: Which is a bed and which is a dargash? R' Yirmeya said: In a bed, one fastens the supporting straps over the bedframe; in a dargash, one fastens the straps through holes in the bedframe itself. The Talmud raises an objection from a Mishnah in tractate Kelim (16:1): With regard to wooden vessels, from when are they considered finished vessels and susceptible to ritual impurity? A bed and a crib are susceptible from when he smooths them with the skin of a fish. And the objection is: If in a bed the straps are fastened over the bedframe, why do I need smoothing with the skin of a fish? The wood of the bedframe is obscured from view.