Many winter sportspeople rent skis and bindings from the ski rental shop, especially when travelling. The binding is a safety component. It should release under a dangerous load and free the foot, but otherwise hold reliably. If it does not release, serious knee and lower-leg injuries threaten. If it opens without cause, a fall can result.
With the rental the ski rental shop takes on a duty. From the contract for work it owes the proper setting of the binding under the recognised rules, for instance the standard ISO 11088, based on weight, height, ability, age and sole length. If it sets wrongly and this leads to the loss, it can be liable. Decisive remains the proof of causation.
This post explains the duties of the rental shop, the role of the setting record and the questions of proof. How liability is apportioned in a collision independently of the equipment is covered in the post on the apportionment of fault under the FIS rules.