| 摘要 |
Disclosed is a sheath that is open at both ends and receives a cap (4) at the lower end thereof, i.e. the end that is embedded in the substrate. Said lower end of the sheath comprises a circular rim (5) which radially protrudes towards the inside thereof and defines an opening. The inventive cap (4) is made of a compressible elastic material and comprises a raised central boss (4a) and a base (4d), the cross section of said boss (4a) being larger than that of the opening. The boss (4a) is provided with a groove (6) receiving said rim (5). The base (4d) of the cap (4) is formed such that said base (4d) engages with the rim (5) when the cap is in a mounted position. |
