This book cushion is made of linen and wool, which were available locally. The woollen yarn is dyed red, blue, yellow and green. The pale and brown strands are possibly the natural colour of the wool. The patterning of the cushion is a red chequered pattern, diagonally positioned. The squares display a geometrical motif which is repeated, with minor variations, all over the cushion. Various colour combinations occur, diagonally shifted, imparting a uniform but still varied appearance to the cushion.
The materials and the regular embroidery technique cause this book cushion to resemble a woven woollen fabric when viewed from a distance. It is very interesting to note that the Uppsala Cathedral collections include a 15th century embroidered altar frontlet with the same motif, re-used as a button placket on a cope. That frontlet, however, is executed in quite a different technique, and using gold thread and red, blue and yellow silk.
Book cushions were used on the altar, to prop up the books used for the different services. They also served the conserving purpose of minimising wear and tear. In addition, the softness of the book cushion underscored the veneration due to liturgical books and the Bible. The Ärentuna cushion is one of very few book cushions to have come down to us, and moreover, it has survived complete with its medieval padding.