The twenty-sixth perek opens by discussing different keilim that are made of simple pieces of leather, but take their form once strings that are looped through them are drawn tight. One example the kis shel shenatzot -- a purse. The Mishnah teaches that any person can make the kli tameh (susceptible to tumah) or tahor by tighten or removing the string -- it does not require a craftsman's involvement. R' Yossi however argues that that is true for all keilim -- they can be modified to become tameh or tahor without an expert's involvement. Instead R' Yossi maintains that what is unique about the keilim listed in the Mishnah is that even if the string is released such that the leather is now flat without any receptacle, it is still tameh since anyone can draw the strings to return it to its original state.

The Mishnah Achrona directs our attention to the Rambam's ruling in the Mishnah Torah (Keilim 7:9). The Mishnah Achrona notes that the Rambam first rules like R' Yossi, that even when the kis shel shenatzot is open, it is still susceptible to tumah. The Rambam however continues that if the straps are removed, if the kli was tameh, it is now tahor even though anyone can return them to their place. The Mishnah Achrona stresses the two parts of the Mishnah appear to contradict each other. How can the de-strapped kli both become tahor and be susceptible to tumah?

The Mishnah Achrona first cites the Kesef Mishnah who suggest that the two parts of the Mishnah are discussing two different things. Removing the straps would indeed make the kli that was tameh now tahor. The first statement of the Rambam however is teaching that it is nonetheless susceptible to tumah going forward, since it can easily be returned to its functioning state. If this explanation is true however, the Mishnah Achrona is at a loss for the source of this understanding.

Instead, the Mishnah Achrona suggests that really there is no debate in our Mishnah and the Chachamim and R' Yossi were discussing two different cases. Both cases are what the Rambam is mentioning.

The tumah status of the un-strapped kli depends on the intent of the owner and whether he wants to re-strap the kli. The Chachamim were discussing where the owner removed the straps. It is now a simple piece of leather, no longer a kli and no longer susceptible to tumah. R' Yossi however was discussing where the straps feel out. In that case, the owner would likely want to put it back together again. The novelty of the keilim in this Mishnah is that in this case, since it is readily repaired, it is still susceptible to tumah.

The Tifferet Yisrael (Boaz 26:1) discusses the position of R' Yossi at length and concludes that there are four different cases. For regular keilim that would require a craftsman to repair them, when they break they are completely tahor. If the broken kli does not require a craftsman and it takes no effort to repair it, like our case, then even in its "broken" state, it remains tameh. If however, only one of these is true -- it requires a craftsman or it requires effort -- then while it is broken, it is tahor but if it is put back together, then the original tumah returns. However, in the previous case, if when the straps are removed it still retains some of its shape, then it is comparable to the second case and is still tameh.

The Tifferet Yisrael therefore explains, the Rambam opened with our case, where it does not require the craftsman and it takes no effort to repair it. In that case the straps come out of the loops but are still attached to the leather. Consequently, it remains tameh. The second case the Rambam is discussing is where the straps were completely removed. In that case more effort is required to repair it and the kli is therefore tahor.