What it does

An equation is drawn on a transparent background, so gridlines, shading and anything else on the sheet show through it. Box gives it a background and a thin black border.

By default the background is taken from the cell the equation belongs to, not simply white. Put an equation over a shaded block and the box matches the shading; over a plain sheet it is white. This is what stops a boxed equation on a coloured table from appearing as a white rectangle cut out of it.

That default, and two other things about the box, can be changed in Settings — see The box settings below.

Box and Lock together

A locked equation is outlined whether it is boxed or not, so you can see at a glance which equations will not be redrawn. Its border is dashed rather than solid.

Box off, unlocked

No border, and the sheet shows through.

Box off, locked

A dashed border, and the sheet still shows through.

Box on

A border — solid, or dashed if the equation is locked — filled with the cell's colour.

The box settings

Three settings under Box in the Settings panel. All three apply wherever a box is drawn — to equations rendered on the Formula tab and to equations written on the LaTeX tab alike.

Padding

How much room is left between the equation and its border: None, Tight, Normal, Roomy or Wide. Measured against the type size rather than in pixels, so the gap looks the same whatever size the equation is set at. The border sits on the edge of the picture, so this room has to be inside it — which means changing the setting redraws the equation rather than simply restyling it.

Background

What the equation is drawn on. Cell Colour is the default and is described above. Choosing a fixed colour instead uses that colour everywhere, whatever the sheet beneath it looks like. Nothing about the background is stored with the equation: it is looked up each time the box is drawn, so an equation over a row that is shaded later picks the new colour up.

Outline

The colour of the line itself. Black by default.

Usage

Box does two things at once. It becomes the setting every equation you render from then on is drawn with, and it is applied immediately to the equations belonging to the cells you have selected.

So to change existing equations, select them — or a range covering them — and then tick or clear the box. To change only the default, tick it with an empty cell selected: there is nothing there to reformat.

If a boxed equation has the wrong background, the cell's fill has changed since it was drawn. Select it and tick the box again, or redraw it.