Assertion: flipper's portion | /r/CapableOf | provide at least two opposed rails
Facets:
value: on each longitudinal edge
type: LOCATION
Source sentences:
text: According to one aspect, the invention provides a swimming flipper comprising a shoe portion and a flipper portion extending therefrom, said flipper portion having provided on each longitudinal edge thereof at least two opposed rails extending outwardly and at an angle to the plane of said flipper portion.