The present invention provides a method for fitting a surface to a point group using computer. The main body has a crisscross groove formed in the main body. The charge comprises a forward end positioned in the opening between the inside diameter and the outside diameter. Another embodiment cross pin retention system includes a pair of locking clips coupled to the cross pin. A female portion of the interface adaptor includes bores that align with the branching feature and support the mounting of nozzles therein. In one embodiment, a line-of-sight volume is a grid volume that has the same size and shape as it corresponding game element.