| 摘要 |
<p>The panel has front grooves (2) exhibiting a form of recesses, boreholes and/or an opening and arranged in reference to rear grooves (1) at a rear surface (B). The rear grooves exhibit smallest depth in an area of a longitudinal edge (1a). The front grooves are arranged according to a longitudinal axis of the panel. The front grooves have a sufficient depth at a front surface (A) to maintain free passages (2a) in an overlapping area or a cross over area between the front and rear grooves. The passages are found in different levels corresponding to depth of the rear grooves.</p> |
