Abstract: A temperature and stretch compensating wire tensioning system. In parallel wire capacitive security systems, the maintenance of proper tension in the sensor wires in essential in order that false alarms be avoided as a result of movement of the sensor wires in the absence of an intruder. In the present invention, "V"-shaped plastic tensioners are used on several of the wire support posts in cooperation with wire guides on other posts to provide the requisite wire tension. The plastic tensioners are constructed from pairs of identical elongated arms each having an open loop at the proximal end thereof adapted to snap onto a support post for easy assembly of a security system in a manner which keeps them perpendicular to the longitudinal axis of the post and directed tangentially away from the outer surface thereof.