Non-hardening electrical putty, also known as duct seal compound or mastic, is the preferred material for sealing wire entries directly inside the box. This practice is a fundamental part of maintaining a structure's envelope. It prevents the uncontrolled movement of air, moisture, and. Hole plugs prevent damage to cable systems and circuitry from dust, debris, and water ingress. They work by slotting or 'snapping' into spare or unwanted openings in electrical cabinets and enclosures. And the control cabinet standard DIN EN 61439 (IEC 61439) stipulates that control cabinets must be equipped with a seamless gasket. Step-by-step guide and expert tips.