For permanently elastic seals for contact and corner joints, passages in walls and floors, drains in pools, tanks and showers. Withstands a wide range of temperatures, salts, diluted acids and alkalis. Permanently elastic rubber strip based on a special polypropylene fabric with alkaline protection, provided with a rubber coating. After the application of liquid paperboard (S-T8) or liquid elastic waterproofing, it creates flexibly sealed corner joints in walls and floors. The system also includes: internal and external corner and elastic grommet.