| 摘要 |
Tongue and groove boards (1) are provided with integral spacers (4) that permit expansion of the assembled boards without buckling, by milling on the bottom of the groove (2) a central longitudinally extending rib (4) of triangular cross section. Spaced portions of the rib (4), of total length that is most of the length of the board, are then compressed to the level of the bottom of the groove, thereby leaving a series of relatively weak projections (4 min , 4 sec , 4''') which serve to space the boards apart the necessary distance during assembly, but which are not strong enough to resist compression upon expansion of the boards under the influence of moisture or temperature. |
