He's going to hem the pants, for example. Until the end of the Perek (chapter), we'll talk about the Shomrim, people who are watching someone else's object. We know that every type of Shomer has his own responsibilities and obligations if something happens to the item he's watching. A Shomer Chinam, an unpaid watchman, would only be obligated to pay for the item if it was damaged because he was negligent in watching it. A Shomer Sachar, somebody who's paid to watch an object, would even be liable if he wasn't negligent—for example, if an item was stolen or lost—but he would be exempt if the damage that happened was unavoidable and had nothing to do with him.
The Mishnah here will talk about a craftsman who's working on an item for somebody. Is he considered to be a Shomer Sachar, a paid Shomer, with a higher responsibility? Or is he like a Shomer Chinam, where he is not responsible for the item he's watching, and only if he was negligent would he have to pay and compensate the actual owner? The Mishnah says: “All craftsmen who work in their own homes or in their own stores, working with other people's items, are considered to be a Shomer Sachar, a paid Shomer, on their own, on the items that they're working on.” For example, let's say you have a tailor. He's given a suit that he's going to fix. He's considered to be a Shomer Sachar on that garment, and therefore he would be obligated to pay for any damage due to his negligence, even if it was stolen or lost. We consider a craftsman to be a Shomer Sachar because he benefits from holding onto the object: he holds onto it as security until he's eventually paid for his services. So he wouldn't return the object until he's eventually paid for his work. He's benefiting by not having to chase the owner down for his payment; he just holds onto the goods. He holds onto the other person's item as collateral or as security until he's paid for his work. So that benefit is enough to consider him to be a paid Shomer. But once the craftsman finishes his job and tells the owner of the item, “Take this item and bring me my fee afterwards,” in other words, what's he telling him? “I'm not going to hold onto your item as security anymore. I don't want to have it here in my store. Take it, and then come bring money and pay me.” During the interim, until the person picks up the item, we say that the craftsman here has the din (law) of a Shomer, of an unpaid Shomer. It changes. He gave up the right, basically, to hold onto the item. He told the owner to come pick it up. He's not going to use it as security anymore, and therefore he doesn't really have any benefit from holding onto it. So he gains, in a sense, because he would now not be responsible if the item was stolen or lost. Only if he was totally negligent would he be responsible. But his, since he doesn't benefit on one end to use it as a security in order to make himself get paid, he gains on the other end, because now he would not be responsible if it was lost or stolen.
Let's say somebody says to his friend, “Watch my item for me today, and tomorrow I'll watch your item for you.” At that point in time, he's considered to be a Shomer, a paid Shomer. He's being paid to watch the other person's item. He's being paid in the sense that his friend is going to watch his item for him. So he's basically trading services over here, but that trading of services is considered to be a payment of sorts. Therefore, he takes on the law of a Shomer Sachar, and he would be responsible for the item being lost or stolen. For a person to become a Shomer, he has to actually accept the responsibility that he's going to guard it. What does the person have to do? The Mishnah says that if a person says to another, “Could you do me a favor? Could you watch my item for me?” and then that person replies back to him, “You put it down before me,” at that point, it's considered to be a Shomer Chinam. That statement implies that he's agreeing to watch the item and taking responsibility for it. If he is negligent, of course, a Shomer Chinam would not be responsible if it's lost or stolen. But that remark, or that line of “put it down in front of me,” is considered to be enough. He doesn't have to say straight up, “I am taking responsibility for it.” That simple line, “Place it down in front of me,” shows that he's assuming responsibility for the item. And therefore, it is now his, and he's watching over it. If he was negligent in watching it, he would be responsible to pay the owner.