Persp/Ortho 

Switch between Perspective and Orthographic projection.

Up X/Y/Z/Free 

Select the "Up" axis for the loaded mesh. By default its Z-up, which is standard among CAD applications, but many popular animation programs use Y-up. So if you load your mesh and its lying on its side, try the Y-up or X-up options to get it up the right way. The Free option turns on free rotation; UVLayout won't try and keep the object upright, and so you can tumble the view beyond the normal camera lock points.

Light Slider 

Move the slider to move the light source from right to left. Click the gray Light button to turn the directional light source on and off. When off, all faces are equally lit, making details in previously dark areas more visible.

X-Ray Slider 

Move the slider to the left to make the mesh more and more transparent. You can use this see, and pick, obscured edges that might be hard to access normally.

View UV/Ed/3D 

Switch between UV edit, 3D edit and 3D textured views. Use the ? hotkey to find out what other hotkeys are available in each mode.

Color Error / 4/5 / Local 

Switch between "flattening error" and 4/5 keys or Local "rescale" coloring of polys when in the UV view.

Trace 

Select Trace to load an image in the background when editing UVs. Use the first slider to fade the background in and out, and the second slider to change the transparency of the flattened geometry. Select Trace a second time to turn the background image off.

Smooth SUBD UVs  [Professional Version Only]  

When turned off, UVs are linearly subdivided when SUBD surfaces are displayed in smooth shading mode. When turned on, UVs are smoothly subdivided; this is equivalent to Renderman's Smooth UVs option. This toggle only applies to the display of textures, and doesn't affect the flattening in any way.

Show Repeats 

Panes

When you first start UVLayout, you only see one view at a time of the loaded object in the display window. You can quickly switch between the UV, Ed and 3D views with the 1, 2 and 3 hotkeys, but if you have a larger monitor, you may want to see more than one view at once.

Split Pane 

This splits the current pane into two. If you only have the single view window up, it'll create two equal panes within that space. Initially the newly split panes have the exact same view, but you can use the 1, 2 or 3 hotkey at any time to change a panes view mode.

Kill All Panes 

Moving and Resizing 

Saving Panes