I am trying to describe that a certain washer prevents or reduces the possibility of a bolt coming off. In other words, I am trying to describe that the bolt usually stops a bolt from coming off, but may sometimes fail to do so. That is, I don't want to vow that that washer always stops a bolt from coming off. If possible, I don't want to use the conjunction "or". Could you advise me on my examples below:
This washer restrains a bolt from coming off.
This washer makes it unlikely that a bolt comes off.