Spark gaps
Spark-Gaps often end in two opposite tracks having pointed tips, maybe triangles. To have electrical sensibility the tips themselves should be solderstop free. Triangles are used, because at their tips the field strength is highest. Spark gaps also can be built as non plated PadStacks in multilayers. This saves space on the board.
For getting an element free of solderstop, please draw e. g. a filled (solid) Rectangle upon the Solder stop layer. This layer is displayed invertedly, that means all what appears in color on this layer later will come out solder free. So exactly this rectangle later will be solderable thus solderstop-free.