The dossal is used where there is no reredos and usually is of the Church color for the Festival or Season.
"The American Church Dictionary and Cyclopedia"
William James Miller
Leaning heavily upon the lady, at the end he won to her maiden's chamber, where there was a fair bed covered with a rich dossal of broidered silk, edged with fur.
"French Mediaeval Romances from the Lays of Marie de France"
Marie de France
Our damsel spread it on the bed, because this dossal is richer than the coverlet that was there before.
"French Mediaeval Romances from the Lays of Marie de France"
Marie de France