They are usually about 2 feet 6 inches (76 cm) high, with a padded step at the bottom, and designed so that the wider top of the rail can support the forearms or elbows of a kneeling person.
Barriers of various kinds often mark off as especially sacred the area of a church close to the altar, which is largely reserved for ordained clergy.
In Eastern Orthodox and related rites, this evolved into a solid, icon-clad screen, called the iconostasis, that has three doorways which usually have doors and curtains that can be closed or drawn aside at various times.
A church in Hasle, Bornholm claims to have "a rare 15th-century altar rail";[6] perhaps, like other examples, this is in fact a sawn-off medieval screen.
Archbishop Laud was a strong supporter of rails, but the common story that he introduced them to England is incorrect; he was trying to prevent Puritan clergy from continuing to remove them, and his pressure in favour of rails was bound up with his very controversial "altar policy", reasserting the placement of the altar in its medieval position.
Wren defended himself against charges of enforcing altar rails, which he pointed out had been found in many English churches "time out of mind".
[9] In both Catholic churches and Anglican ones following Laudian instructions, the congregation was now asked to come up to the rails and receive communion kneeling at them, replacing a variety of earlier habits.
Many Catholics resisted the changes: some took legal action to try to prevent the removal of altar rails and of other traditional features in pre-Vatican II sanctuaries.
In recent times, a number of restorations of historic churches have re-introduced altar rails, since the idea that Vatican II required their removal is a misconception.
[15][16] The General Instruction of the Roman Missal states explicitly that the sanctuary "should be appropriately marked off from the body of the church either by its being somewhat elevated or by a particular structure and ornamentation".