Preformed part has first edge provided with protruding tongue with rounded section and second edge with groove with undercut, whereby rounded section of tongue of one preformed part fits into undercut in another second preformed part

摘要

The preformed part (1) has a first and second end edge (3',3"), with means for locking of the end edge of a first preformed part on the end edge of a second preformed part. The first edge has a protruding tongue (30) with a rounded section (31), while the second edge has a groove (32) with an undercut (33). The rounded section of the tongue of one first preformed part fits into the undercut in another preformed part. The edges of the first and second preformed parts may have holes to receive spigots on a connecting plate which may interconnect the two preformed parts.