preventing the drain from sinking slightly below the concrete surface or raising slightly above it while the drain in the present invention is shown as having a rectangular body and more particularly a square body it may of course be circular and two or more clamp bars may be utilized which or course would be semi circular or otherwise correspond to the shape of the body of the drain while the clamp bars shown in the drawings have been shown as being affixed by a plurality of studs and coupling nuts other affixing means may be used such as one or more springs or other clamping assemblies it is highly desirable however that the clamping assembly not provide any further opening in the rim 15 of the drain body as this could cause another source of seepage which is eliminated by the assembly shown in the drawings furthermore the clamping system should not require a hole in the membrane or in the flange itself as this could also provide a liquid path outside of the drain body and bottom outlet while the studs 25 are shown as welded to bars 24 it would of course be possible to weld the coupling nuts 26 to the bars and provide some turning means such as.