הלכות כלים

There are three categories of wooden implements that are not intended to serve as containers:
a) Any wooden implement that is made solely for human use, e.g., a ladder. It is pure. It is not susceptible to impurity at all, nor did our Sages decree that it should be included among the implements susceptible to impurity.
b) Any wooden implement that is made to be used for other implements and by a human, e.g., a table, a counter-top, a bed and the like. They are susceptible to ritual impurity. How is it known that they serve both a person and his accessories? Because one places plates on the table, cups on the counter-top, and spreads on the bed.
c) Any wooden implement that is made solely for the use of implements; thus it serves entities that serve man. If it only serves other implements during the time work is being performed with them, it is entirely pure, e.g., a wooden candelabrum that serves a lamp while it burns.
Similar laws apply to an implement placed under an implement while it is being used and all molds. If, however, it serves implements during the time work is being performed with them and when work is not being performed with them, they are susceptible to ritual impurity. Examples of such implements are: the covering for a box and the like; a sheath for a sword, a knife, a spear, scissors, a razor, a spoon used for blue eye paint, or a stylus used to write; a well used to store blue eye paint; a case for a writing tablet or a leather placemat, a carrier for arrows, a case for wide arrows, and a case for flutes. All of these and anything like them are susceptible to impurity even though they are only used to serve other implements. The rationale is that they are necessary for the implements both at the time work is being performed with them and also when work is not being performed with them.
There are, by contrast, other somewhat similar implements that are pure, for example: the covering for a wardrobe, the covering for a chest, the covering for a basket, a carpenter's press, a chair placed under a chest or a domed covering for it, the mold over which a leather covering for a Torah scroll is made, a wooden covering for a door bolt, or the covering for a latch or a mezuzah, a case for lyres and harps, a bust on which the makers of turbans wrap that head-covering, a mold on which tefillin are made, a wooden horse used by a singer, rhythm sticks used by mourners, a sun-shield of a poor man, support beams for a bed, the pillars of a bed, and a board used as a support for a bed. All of these and implements like them are pure, because they serve other implements only when they are being used.

With regard to the headboard of a bed: if it is capped and has legs that are connected to the bed, it contracts impurity together with the bed, because it is placed at the head of the bed and it is considered as one of its components. If it was placed on two of the bedposts, and thus it is higher than the bed, even though the headboard is tied to the bed with cords, since it does not have feet, it is pure. The rationale is that the headboard only serves other implements at the time work is being performed with them, like the hanging boards of the Levites, upon which they would hang their harps and their instruments, which are pure.

A press used by shoemakers over which leather is pulled tightly is pure, because he places the stone in the hollow inside of it and uses it. Thus it is made to serve implements only at the time work is being performed with it. It does not contract impurity because of its receptacle, because the hollow within it is meant to be filled with a stone.

The coating of a bed is pure. Similarly, any ornamental covering - whether it is made from wood, bone, leather, or metal - is pure. This concept is derived from Leviticus 11:32 which states "with which work will be performed with them." This excludes the ornamental covering of implements.
Similarly, a wooden or bone implement that has a receptacle, but which was plated with metal is pure and it is not susceptible to impurity. The rationale is that the plating causes the implement itself to be considered insignificant and the plating itself is pure, as explained.

The following rules apply when a person makes a utensil partially of wood and partially of metal. If the wood serves the metal, it is susceptible to impurity. If the metal serves the wood, everything is pure.
What is implied? If a key was made of wood and its teeth - or even one of its teeth - were metal, it is susceptible to impurity. If it was metal and its teeth, wood, everything is pure.

When there is a tooth from a key or a signet of metal, it is susceptible to impurity independently if it was not connected to wood. Similarly, if one of the wooden teeth of a pitchfork, a farming prong, a winnow or a comb for a girl's head was removed and replaced by a metal one, the implements are susceptible to ritual impurity.

When a metal projection shaped like a pomegranate was placed on a wooden staff to use as a handle, it is not susceptible to ritual impurity. If the staff was made with a metal cap so that the earth would not destroy the wood, it is susceptible to impurity.

Similarly, if spikes were affixed to a stick to use as a weapon, it is susceptible to ritual impurity, for the wood is serving the metal. If they were placed there for decorative purposes, it is not susceptible to ritual impurity, for the metal is serving the wood.