{HEAD ~ Spirit level extenders} 9 have a pair of opposite inwardly directed longitudinal female dovetail flanges 17 for engaging {TAIL ~ a spirit level} clamp 11  
{ HEAD ~ Spirit level extenders } 9 have a pair of opposite inwardly directed longitudinal female dovetail flanges 17 for engaging { TAIL ~ a spirit level } clamp 11
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH