On their free ends, they are provided with {HEAD ~ inwardly projecting snap noses} which engage {TAIL ~ a recess} of the sabot 
engage
On their free ends , they are provided with { HEAD ~ inwardly projecting snap noses } which engage { TAIL ~ a recess } of the sabot
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH