A Stainless Steel Side 3x Adjustable Roof Hook. Van der Valk Solar Systems is a specialised enterprise that is fully focused on developing and producing solar mounting systems. The efficiency of solar panels is highly dependent on the mounting system in which they are employed and it was with this in mind that Van der Valk Solar Systems decided to specialize entirely in this area. The results of this can be seen in the systems on offer, which vary a great deal in terms of sustainability and ease of assembly.