I've read the TM and searched, but can't find the purpose of this U-channel bracket on the newer metal bows. I took them off, and the bows stay in place, I tried to adjust them to raise the bow height, but no go. One bolt is in a hole and the bottom is in a slot in the channel and hole in the bow upright. In the photo, you can see where I've removed the U-channel on the bow on the left. Just wondering if anyone has an idea what they're used for?