The resizing constraints in the Inspector let you choose how layers behave when you resize the Artboard, group or symbol they’re a part of. To set resizing constraints, select a layer within an Artboard, Group or Symbol to show the resizing constraints controls in the Inspector.
The controls on the right set which edges of a parent your layer will pin to, while the controls in the middle set whether your layer’s height and width should stretch or stay at a fixed size. On the right, there’s a preview to show how the controls you select affect your layer’s behavior.
Tip: By default, we’ll resize layers within a Group or Symbol relative to their parent, including any padding.
If you want a layer to resize relative to the Artboard it’s a part of, select the Artboard itself and check Adjust content on resize in the Inspector.
The Fix Size constraints keep a layer’s height or width (or overall dimensions) the same, no matter how its parent is resized.
This is useful, for example, if you have a menu bar in an interface that you want to keep the same height, no matter how tall the Artboard it’s in becomes.
Pin to Edge
Pin to Edge fixes the distance between a layer and a particular set of edges or corners of its parent, no matter how the parent is resized.
This is useful, for example, if you have a floating action button within an interface, pinning this to the top and left edges will make sure it stays the same distance from the corner of an Artboard.