This is a simple signal capable of displaying either STOP or RESTRICTING (as STOP-AND-PROCEED). This type of signal is typically found where movements in its direction are fairly infrequent, or where a dwarf signal with proper dwarf with block-signalling capability is not justified, such as at yards, on industrial tracks, entrance to a mainline, or at mainline interlockings for traffic running against the current-of-traffic in Rule 251 territory. In unsignalled territory or when used against the current-of-traffic, place an invisible signal at some point beyond this signal facing the same direction and it will display RESTRICTING.