The ceiling of the church is a decorative stone rib vault. Where the ribs meet in the middle are decorative roof bosses of which there are a number of different designs, including a Green Man, which is usually considered to be a pagan symbol of fertility. In the Christian church the Green Man is often used as a symbol for Easter and the Resurrection. The central boss shows a staff over a tun (barrel) to represent Abbot Overton, who was Abbot of Crowland from 1392 to 1417. Two more bosses show letters ‘IHS’, which is the Greek abbreviation for Jesus and the word ‘Alla’ which is short for alleluia.