A tensioner for applying force to a device to be tensioned is configurable for applying force in different directions and comprises: a mounting plate having a guide; a slidable member slidable relative to the guide of the mounting plate for receiving a support for a device to be tensioned; a spring for being coupled to the mounting plate and to the slidable member, wherein the spring urges the slidable member in one direction when coupled to the mounting plate and to the slidable member in a first configuration and urges the slidable member in an opposite direction when coupled to the mounting plate and to the slidable member in a second configuration. The tensioner configurations enable the tensioner either to pull or to push the support for the device to be tensioned.