Snap Anchors is a simple Unity asset that allows you to snap the anchors of your UI elements to their appropriate corners.After downloading and installing the package, just right click the UI element in question, the option "Snap Anchors" should now be available with two variation "in this" and "in this and it's children", the first option will only snap the anchors of the selected element, the latter option will snap the anchors of the element and all elements under it.
If you have any questions or doubts please E-Mail me at rodrigodtoni@gmail.com