Keith wrote:
What I want to do is to make a rounded corner (one of the corner) on a rectangular drawing and be able to adjust the curveness of the corner.
Turn on the Grid, and Grid Snap
Custom Shape Tool
Quarter Circle Shape
Set the radius to what you desire
Draw Quarter Circle Shape
Free Transform the layer (or two 90 deg. rotations) to rotate this corner to the orientation you need
Move the Quarter Circle into the corner — it should snap there Draw 2 rectangles with the shape tool so that you cover the area "not corner" (you’ll see white everywhere except for the corner where your picture shows thru)
Turn off the background layer
Merge visible layers (3 layers with shapes)
Turn on the background layer
Double click your background layer and change to Layer 0 Move Layer 0 over the shape so you can move it over the shape layer Group background layer with shape layer
The grid will help you draw and place the shape with precision You can adjust the quarter circle roundness up till the point where you merge the shape layers.
Ed