The wheels are made of metal and will not be cut or damaged by the frame cables. With this tool, it is possible to fix very easy and very fast cables or stainless steel wires to the frame. You need place the cable between the two gears, hold the spring and straighten the cable tension. When you put it on the whole cable, hold it firmly, and then pull the cable, it will crimp the cable and can be moved immediately.  This tool is designed for users who still use traditional manual pull cord shelves.    Item Name: Tensioner Material: Plastic, Metal Features: Durable, Beekeeping Tools, Tight String Wire Size: 13.5cm x 4.5cm x 1cm/5.31" x 1.77" x 0.39" (Approx.)   Notes: Due to the light and screen setting difference, the item& 39;s color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.   Package Includes: 1 x Tensioner