Truss rod nuts/bolts often require a substantial amount of torque to turn, so a wrench that doesn't fit properly is either going to get wrecked itself, wreck the fastener, or both. Once that's done, it becomes a waking nightmare trying to fix it. I just went through that repairing an older neck where one of the owners somewhere along the line tried cheating with wrong tool, and it was no fun at all. If you can't find the right tool for the job, keep looking. Anything less is almost guaranteed to cause you grief.