These Shower Door Thresholdsare mounted directly below the shower door to let the water drain back into the shower stall. Ideal for flat or out-sloping curbs, the rounded low contour of the Half Round Threshold will not harm feet. The Tapered Style Sill leaves a minimal sightline from the exterior of the shower. These thresholds may be used in conjunction with a bottom sweep. Use Mildew Resistant Silicone Sealant to adhere to curb of shower stall.