Square cut in the bedrock (and partially SU555) of unknown function - possibly for a beam or support of some kind. It is in line with and the same shape as the nearby cuts SU567 and SU568 (see sketch), which appear to be related to it. The cuts are quite close together (ca. 35cm apart), so perhaps the supports could be moved or adjusted. Related to nearby quarrying activity? This arrangement is very similar to the nearby cuts SU533, SU547, SU549, just to the S.