Anchoring is the act of locking an element to the side of your canvas. When an element is anchored in one size, all sizes that are activated later using that size as their reference point will also leave that asset anchored to that side of the canvas. This helps make the automatic formatting of elements in Flexitive better when you activate additional sizes, and will reduce the number of minor changes that you will have to make.
To anchor an element, drag the element to one or more of the edges of the canvas. When you have anchored an edge of the element, the bounding box on that corner of the element will change from green to red, as shown below. You can anchor an element to as many edges of the canvas as you like.
If you would like to anchor all edges of your element to the canvas, you can use the Snap to All Edges button in the Customize panel on the left-hand side of the screen. This will automatically expand the bounding box of the selected element to anchor to every edge of the canvas. Pressing Snap to All Edges with a text box will change affect the line breaks of your text but leave the font size and styling unchanged.