The invention relates to a system for sealingly holding cables through an opening. The system comprises a holder substantially in the form of a plate having a central portion with a first thickness between a first side and a second side of the plate and a peripheral portion with a second thickness which is smaller than the first thickness, the holder having in the central portion a plurality of conduits extending in the thickness direction of the plate, each conduit being suitable for having one or more cables extending there through, at least one multi-part sealing plug of an elastic material for sealing an annular space between an inner wall of one of the conduits and a cable extending there through and a gasket of an elastic material and of a shape for placement against the peripheral portion so as to provide a sealing in a circumferential direction of the plate. The plug has at least one circumferentially extending outer rib and at least one circumferentially extending inner rib. In an uninserted state, the following conditions apply: the outer rib has a sawtooth shape for easy insertion, the sawtooth is provided with an angled inward bend for facilitating flexing of the sawtooth in a transverse direction, the inner rib has a top surface extending in circumferential and longitudinal direction for facilitating sliding along the cable, and an imaginary straight line extending in a transverse direction coincides with a pivotal point of the angled bend and intersects the top surface.