A beacon comprising a staff and ball is shown at the center of the linear reef of Woolhouse Rock. Sailing Directrions dating to 1884 note 'Upon the centre of the rock is a pyramidal beacon of masonry, surmounted by a staff and ball, the entire height above the base being 59 feet.' For mariners, aligning the beacon with the Monkstone near Trevane allowed them to avoid the Drift Rock and the Spaniel Shoal.

Sources include:
Admiralty; 1884, Sailing Directions for the Bristol Channel, 4th Ed, pg78
Historic Admiralty Chart OCB1165-C1, RCAHMW Digital Collections sourced from the UK Hydrographic Office and published in 1888

Maritime Officer, RCAHMW, September 2014.