Commentaire sur Kéilim 17:16

קנה המאזנים (the beam of the balance) – The deceivers make it hollowed out and place in the hallowed out section, pure silver, and when they weigh it, it diverts/perverts the beam a bit and the live silver goes to the side of the thing that is being weighted and makes it heavy and overwhelms it.

The beam of a balance and a leveler that contain a receptacle for metal, carrying-stick that has a receptacle for money, a beggar's cane that has a receptacle for water, and a stick that has a receptacle for a mezuzah and for pearls are susceptible to uncleanness.
About all these Rabbi Yohanan ben Zakkai said: Oy to me if I should mention them, Oy to me if I don't mention them.
Sections one and two: All of these vessels are various sticks or things like sticks that can contain other things and are therefore susceptible to impurity. In addition, each could be or is generally used for a negative purpose. The beam of a balance that has room to hide metal in it can be used to deceive a buyer by tilting the scales. A leveler is used to level out measuring cups. A person could make a receptacle in the leveler in order to skim the tops of the cups and cheat the buyer.
A carrying-stick with a hidden compartment for money could be used by a worker to deceive his employer into paying him a second time. I.e. he could say search me if you find the money on me, then you paid me.
What's wrong with a beggar's cane that has a receptacle for water? The Rambam explains that the beggar can claim that he has not been drinking so that people will have pity on him.
The sticks that have a receptacle for a mezuzah or a pearl could be used to cheat a tax collector.
Albeck explains that while all of these things also have legitimate uses, since they can be used deceptively, Rabbi Yohanan ben Zakai laments having to mention them. In other words, he has to teach these halakhot because these vessels can be used in a legal way, but he wishes he could forget about them.

והמחוק (an instrument for levelling a measure of grain/a strike) – that blots out the measurement when it is heaped up. But if they make it of gourds/cucumbers and similar things like it from the light things which lighten it and are bad for the seller, but if one makes of metal which makes it heavy and bad for the purchaser. But one makes it of olives and nuts and of box-tree/ebony tree. But the deceiver makes the instrument for levelling a measure of grain of olive and of hallowed out nuts, and when he sells it, he brings in metal in order that it would be made heavy, but when he purchases, he removes it.

והאסל (a carrying yoke – in which there is a hidden receptacle for money) – a balancing pole/staff that they carry it on the shoulder. But when there are many workers, after he has received his payment/compensation, he places the compensation in the receptacle that is in the balancing pole/staff, and states to the house owner (i.e., the boss), “You did not give me my compensation,” and when they search him, they don’t give attention to search there [in the carrying pole].

קנה של עני שיש בו בית קבול מים – and he drinks from them, and when they ask him if he tasted anything, he states, “I am fasting today.” But My Rabbis explained, a receptacle for water is a receptacle for liquids, and when he is busy [with his work] with the owner/the boss in the olive press, he steals from the oil there.

מקל שיש לו בית קיבול מזוזה ומרגליות – and they use them as such in order to steal in it the taxes/tolls.

אוי לי אם אומר – perhaps/lest that people learn from me to deceive [others].

אוי לי אם לא אומר – perhaps/lest the deceivers will say that the Sages are not experts in the work of our hands, and through this they will come to deceive even more. And why did he say [these things]? Because it is written (Hosea 14:10): “For the paths of the LORD are smooth; The righteous can walk on them, while sinners stumble on them.”