Not completely sure what the question is. It doesn't need to grab onto anything. Let it go where it wants to go. As noted, inch-long protosquash that turned yellow and fell off are just female flowers that didn't get pollinated. If you have male flowers (without the protofruit) and females (with them), hand pollination is easy and works well.

I let my vines fall off of the raised beds and trail around in the veggie patch. I tie a piece of twine to a stick and the other end of the twine to the vine and train the vine to go where I want it to go by placing the stick in the ground where I want the vine to go. Hope it makes sense. Otherwise I can take a pic next time I'm in the garden.

About the female flowers dropping off, I don't believe it is due to lack of pollination. I've had the same issue. Tiny fruits turn yellow and fall off BEFORE the flower on top of it opens. So it had no chance of getting pollinated. If it ever opened i would hand pollinate. I haven't figured out a reason why. No solution there. But there are fruits getting bigger on the vine so I don't worry too much about the ones that fall off.

My experience with butternut is that the plant gets huge. I'd say better to let it trail over the rocks than to try to wrap it as the leaves will get more sun by trailing. I think I had a dozen or so squash from my one plant so be patient and take care not to step on the squash as they tend to blend a bit with the foliage.

Agree with the others. Trying to contain a butternut and its vines to a limited area is futile. It will go where it wants. I don't understand about the raised bed sitting on top of a rock bed but if that means the squash will be laying on rocks you will want to put a layer of straw mulch or something under them.

Dave

I've been using the following technique for butternuts for several years and it works great. I have a non raised but permanent bed garden and I can't handle an immense butternut wandering everywhere. Also, I visually inspect every single leaf throughout the growing season about twice a week for squash bug eggs. Here's what I do. When I can see that there is a good fruit set and the vines are getting to the 5 ft length, I cut off the growing tips of the vines, and any side vines that are starting. This keeps the plant in bounds and makes the leaf inspection not quite so daunting. I get great squash and have gotten as many as 18 butternuts from two vines growing in one hill.