Cover on winter wrap

We wondered, when we put the winter wraps over the hives, whether the covers, which rest a bit precariously on top of the wraps, were sufficiently secure for winter weather? They fit over side to side, but not front and back. We put several bricks on the top of each top, hoping the extra weight would keep the covers in place. But... sure enough...the yellow hive's cover slipped forward an inch. This week, I will figure out how to keep the covers securely in place, perhaps with braces; tapes and ratchets around the hives would do the trick, too.