rood-altar

It was a lofty stone wall, against which stood the altar of the holy cross, or rood-altar, as it was more commonly called, and upon it was a gallery called the rood-loft, from its containing the great rood and its attendant images.

Bell's Cathedrals: The Cathedral Church of Gloucester [2nd ed.] A Description of Its Fabric and A Brief History of the Espicopal See

It seems probable that in some cases the rood-altar was on the loft itself, instead of beneath -- e.g., at

The Catholic Encyclopedia, Volume 13: Revelation-Stock 1840-1916 1913

In churches where there were both pulpitum and rood - screen the latter usually had two doors, and between them was placed, on the western side, the rood-altar, which, in monastic churches, often served as the parish altar, the parishioners being accommodated in the nave.

The Catholic Encyclopedia, Volume 13: Revelation-Stock 1840-1916 1913

A rood-door was either the central door of a rood - screen or one of the two doors on either side of the rood-altar.

The Catholic Encyclopedia, Volume 13: Revelation-Stock 1840-1916 1913

A special altar, called the rood-altar, used to stand under the screen.

English Villages 1892