Profile to form a watertight screen in the ground and method of disposing the same

A sub-surface watertight barrier to prevent migration of liquid therethrough so as to isolate material on one side of the barrier from material on the other side of the barrier comprising a pair of sections each of which includes a main body portion of thin, flexible sheet material having male and female interlocking means respectively along opposite side edges thereof, each of said male interlocking means comprising a flanged portion along one side edge of the associated sheet and presenting a pair of flanges projecting outwardly from respective opposite sides of the associated main body, each flange defining an undercut trough, each of said female interlocking means comprising a hollow portion along the opposite side edge of the associated main body and presenting a recess having inwardly turned flanges at the entrance thereof and defining undercut troughs therebehind, the female interlocking means of one of said sections receiving the male interlocking means of the other of said sections in dovetail interlocking fashion to provide an intimate fit between said last mentioned male and female interlocking means, the terminal ends of said inwardly turned flanges of the female interlocking means of said one section being disposed closely adjacent opposite sides of the thin flexible sheet material of the other of said sections, the bottom of said recess of said one section defining a further trough spaced from the associated inwardly turned flanges to define a clearance space between said interfitting male and female interlocking means, and sealing means applied to the interior of said recess in said further trough thereof for sealing the dovetail interlock between said sections.