In order to make milking the cow easier, I built this head stanchion. The diagonal board slides up into place and when it’s vertical, there is a 1-in hole drilled through all three boards. The front and back sandwich boards are 2x6s as is the diagonal sliding board. I had planned on sliding the board into place and then inserting a bolt through all three holes to lock it in place. She’s too fast for me, and backs her head out knocking the board out of place before I can get the bolt through. I tried looking for spring-loaded plunger latches, but none of them are long enough or thick enough. I’m not married to the idea of using some sort of spring-loaded mechanism, but I will certainly entertain. Any idea that might make this easier. I’m not married to the idea of using some sort of spring-loaded mechanism, but I will certainly entertain any idea that might make this easier.

Any ideas on how I can accomplish this? Thank you in advance