I have had dock locks ( wheels also chocked ) save my bacon on a few occasions when the driver left his tandems forward.

While unloading a trailor I have had the trailor move ( the tandem slipped and the wheels stayed where they were ) The dock lock kept the trailor from moving far enough out to drop the leveler and I was able to get off the trailor without incident.

I would greatly prefer that the drivers make sure that their tandems are all the way back prior to dropping their trailor or backing up to my dock. ( the tandem cannot slip back if it is already all the way back ) Some companies require this but there seems to be no teeth in it.

just my.02