Inkscape is used to draw on a computer. The light gray silverpoint values will darken with time as the silver tarnishes from gray to black. You have to use an eraser and to carefully delete the lines. The drawing grid is an useful drawing tool for beginners ... To erase the grid lines is the hardest part. A good drawing software should ideally have a wide range of colors in the palette. Notice Cookie. Technically, faces are erased after their bounding edges are erased, which enables you to open and otherwise reshape your geometry, as explained in this introduction to drawing basics.However, SketchUp does have a workaround — the context menu's Erase command.)