Device for measuring tension force in web alt. wire without giving any permanent affect on the measured object (7). In goods transportation it is common to use webs to tie down (lash) the load to the load carrier. Then it is important that right pretension force is applied to achieve a safe transport. The aim is to be able to check this force before but even during the transport. This wish is solved with a hand carried device that can be moved across the measured object (7) from the side, perform the measurement after activation arm has been pulled and be removed after deactivation without having any remaining affect on the lashing. Technically this is done when the activation forces the object (7) to bend over a number of rolls (17, 18). This bending calls for a force perpendicularly to the web/wire (7) that is registered, recalculated (calibrated) and displayed as the searched force in the object. To achieve high accuracy the instrument is equipped with two widthsetters which correct set allows exact positioning sidewise of the measured object and a device that can be adjusted and compensates the force for the free length of the object (7). Besides the instrument has an automatic power control which alarms when the battery must be changed.