Many Orthodox Jews touch the mezuza upon entering or leaving a home, sometimes accompanying the gesture with a touch to their lips in a simulated kiss.

Traditionally, Jews are expected to affix a mezuza to the right side (when viewed from the outside) of a door frame at approximately shoulder height, tilted inward. Ideally, they should do so upon moving in, but most Jewish authorities allow 30 days because, historically, Jews had to move frequently and under duress and were often unsure where their permanent home would be, said Rabbi Andy Bachman of Congregation Beth Elohim, a Reform synagogue in Park Slope, Brooklyn.

Jewish law commands that every inhabited room have a mezuza on the door, but many Jews in America today put them only on the front door.

Jews leaving a home are expected to leave the mezuzas behind if they believe the next residents will also be Jewish. If not, they must take the mezuza with them, to guard against the possibility that a non-Jew might desecrate it, knowingly or not. If a mezuza becomes too weathered, dirty or otherwise damaged, it is to be buried, as are all sacred documents, a service that a rabbi or synagogue can facilitate.

Non-Jews, naturally, are not bound by these customs, but many follow them out of deference. Alex Cohen of Borough Park, Brooklyn, who sells, installs and inspects mezuzas under the business name Mezuzah Man, said he had answered calls from non-Jews asking him to remove their mezuzas. The mezuzas should be handled respectfully, he said: “You don’t just put it in the garbage.”