You can resize an individual layer, or simultaneously resize multiple layers to make them the same width and height.
If the Prevent Overlaps option is on, you will not be able to resize a layer so that it overlaps with another layer (see Preventing layer overlaps).
The arrow keys move the right and bottom borders of the layer; you cant resize using the top and left borders with this technique.
For information about setting the grid snapping increment, see Using a tracing image.
Resizing a layer changes the width and height of the layer. It does not define how much of the layers content is visible. To define the visible region within a layer, see Setting layer preferences and properties.
The first selected layers conform to the width or height of the last selected layer.
The values are applied to all selected layers.