A Torah ark is built into or against the wall of a synagogue that faces Jerusalem, so its construction is architectural as much as it is furniture making, carved wood or stone doors set into a recess, fronted by a curtain called a parochet that is frequently the most elaborately embroidered textile in the building.
Construction and craftsmanship
The parochet is commissioned separately from textile artisans, often embroidered with verses, family names as memorial gifts, or symbols like the tablets of the law, and is changed for different occasions, a more festive curtain for holidays than for ordinary weekdays. Ancient synagogues sometimes used a portable ark, a chest that could be carried in for the Torah reading and removed afterward, a form later replaced by the fixed built in cabinet nearly universal today.
Who is allowed to open it
Opening the ark during a service is considered an honor assigned to a specific congregant rather than something anyone present may do freely, and in many congregations this honor is given out deliberately, to mark a simcha or to include a guest. The ark itself is not consecrated the way a scroll is, but it is treated with the seriousness architecture reserves for a focal point, kept locked outside of services, and a synagogue that closes permanently will arrange for its scrolls, and often the ark itself, to be transferred respectfully to another congregation rather than left in an empty building.