A silver halide emulsion including silver halide grains and a binder and satisfying Requirement of 0<BA<0. The dope application nozzle is arranged at a distance from the rotational axis of the top, said distance being larger than the radius of a thread section to be doped. The embedder is implemented to select how many times the derivation function is to be applied to the initial value. The nut has a threaded hole for passing the head of the roof bolt therethrough, for threading onto the threaded spacer and for tightening onto the threaded spacer until the roof plate is firmly pressed against the roof.