An FPCON level may also be designated as "+", meaning the facility shall institute extra security measures beyond those specified for the FPCON Level. Generally this is used to provide an extra layer of security for FPCON Alpha. There is a list of extra security measures that may be initiated for a "+" security level; normally the facility Force Protection NCO will choose two or three for his installation, and switch them out randomly to prevent predictable response. Some, however, are nearly always used. For instance 100% ID checks of all incoming persons is nearly always used at FPCON Alpha+, while armed fenceline patrols may be done for two days, then stopped and replaced with anti-surveillance measures to increase randomness and decrease predictability of defense.