Selflok Old Colonial Smooth Selflok Weatherboards have a super simple self locking system that aligns every board perfectly. Precise routing gives the product a beautiful and unique ship lapped profile which has become the all time Weathertex favourite. Apply the Weathertex concealed joining system to match the seamless lines Selflok offers. Selflok Old Colonial Smooth board has a smooth flat surface finish. The 300mm board contains two 40mm grooves. The groove begins rather deep at 5mm. Gradually, as the groove progresses, the depth decreases, eventually meeting with the smooth surface. When the following board is placed above the previous, the second groove is complete.