Radar reflector

A passive reflector of radar emissions, usually made of
three plane surfaces meeting at right angles to each other. The result forms
eight three­-sided funnels. Such reflectors are mounted on buoys and beacons so
that ships equipped with radar can locate them. Any private craft, of whatever
material of construction, should carry a radar reflector if she moves in waters
where she may encounter ships. The reflector should be as large as feasible,
and certainly not less than 15 inches, and preferably at least 18 inches,
across the diagonal. The reflec­tor should be hung from three of its corners,
so that one ‘funnel’ faces up to the sky as if to collect rain. That will leave
six funnels to face outward around the horizon.