A strainer for straining a length of material, the strainer including a tensioning device configured to tension a length of material between the strainer and an object, characterised in that the strainer includes a conductive component configured to contact the length of the material when held by the tensioning device, and wherein the conductive component includes an attachment portion for an external conductive link to the strainer. This invention also relates to a security system and its method of preparation using the strainer as described herein.