Set the values you want to apply, then click on Move, Scale or Rotate to transform all picked shells. Click the - or / buttons to do the inverse transform. If you want to apply the transforms to one or more boxes and their contents, pick the boxes by LMB clicking on one corner. If no shells are picked, all unlocked flattened shells are modified.

If you want to quickly move shells around by tile units, click the N, E, S, W or diagonal buttons to move them in that direction. Click the C button to center shells within a tile.

The Pivot options are Origin (rotate/scale around the world origin u=0, v=0), or Shell (rotate/scale about each shell's pivot point ^*), or Tile (rotate/scale about the center of the tile that each shell is currently in).

^* A shell's pivot point is the center of its bounding box by default, or the average location of any points that are pinned on that shell. So for example, if you want to rotate or scale about a specific point, use the P hotkey to pin just that one point on the shell.

Use the Reset button to reset the field values back to their defaults.

The three green buttons to the bottom left represent the left, middle and right mouse buttons. By default these are all on, indicating that you can rotate (left), translate (middle) and scale (right) shells by holding down the Space key. Click on any one of the green buttons to turn that function off. For example, if you don't want to accidentally scale any shells, click the third button so it turns gray.

Align To Axes/Vertical/Cam 

Rotate selected shells so that, on average, their polygons are aligned with the U and V axes, or vertically within the 3D space, or vertical relative to the current 3D view camera.

Rescale U & V 

Use these buttons if you want to rescale shells so that their size in UV matches that in 3D. For example, if you load an OBJ with existing UVs and some shells are red and others are blue, clicking on the & button will rescale each of them up or down until they are closer to green in shading. Click on the U or V buttons if you only want to scale in that direction. As with the other transform buttons above, the rescale will only affect picked shells, or all unlocked shells if none are picked. [Example]

As A Group 

Tick this option and all selected shells are scaled by the same amount, and around the center of the group bounding box. This keeps them the same relative size and in the same relative position to each other.

Fit To Sqr 

Use these buttons if you want to rescale shells or boxes so that they fill the UV square. Clicking on U will rescale the picked shells or boxes equally in the U and V directions, but so their widths fit the square. Clicking on V will also rescale equally, but so their heights fit the square. Clicking on | will rescale equally so that the picked shells or boxes fit completely within the square. And finally, clicking on & will rescale unequally so that both the widths and heights fit the square. By default everything will crowd into the 0 to 1 UV square, but if you enable the Pack tool's "Lock All To Tile" option, then each rescaled shell or box stays in its current tile.

As A Group 

Tick this option and all selected shells are fitted to the tile as a group. This keeps them the same relative size and in the same relative position to each other.

Clicking the Fit To Sqr button itself launches a combined Pack and Fit over all of the UV tiles. Unlike the buttons just described, which fit individual or grouped shells to a single UV square, this one operates on all selected shells over all UV tiles. If no shells are selected, all shells are fitted. [Example]

By default, the & option indicates that its OK for the affected shells to be scaled up or down to fit the tile. However, if you select < then the fit for any one tile will succeed only when shells need to be made smaller, and selecting > means shells will only ever be made larger.

Also note that the Pack tool is used, so the current pack settings apply. If rotations are turned on, then the total allocated search time is divided equally among the number of tiles being fitted.

Fit To Grid 

Use these buttons if you want to rescale shells so their bounding boxes are aligned perfectly with the current snapping grid. Clicking on < will always make shells smaller to make them fit to the grid. Clicking on > will always make shells larger to fit. Clicking on | will resize shells to the closest grid line (i.e. they can be scaled up or down).

Set Size 

When an object is loaded into UVLayout, the surface area is computed and an initial real-world to UV scaling is decided upon so that the flattened out object fills the UV square. When the UV shells are packed, this scaling is also adjusted. The current UV scaling is shown in the Set Size field, and it is the size of the UV square in real-world dimensions. You can edit this value to set the current size of the UV square if you wish; remember to type Enter to make any value changes active.

Green Balance 

If one or more of your shells are red or blue tinted for whatever reason, click this and all shells are adjusted so that the average of the selected shells is green (i.e. at the "correct" scale). If no shells are selected, then the scale of all visible shells is used to determine the average value. [Example]