Arty types; how would you iconise/symbolise null/nothing?

Cafe Society
1

I’ve just been given an interesting task; to design a couple of little glyphs or icons; one of them needs to mean ‘mark current row’ (which I think I can handle), the other needs to be ‘remove marks from all rows’.

Now the first one, I can probably do, because marked rows are marked with a symbol and this symbol can be used in the glyph, along with a plus sign or something.
But how do I convey the meaning ‘when you click this, ALL marked rows will be unmarked’ - it’s a bit like designing an iconographic sign for ‘this room contains nothing’ - it’s comparatively easy to create one for ‘this room contains dangerous machinery’, or ‘this room contains a bed’, but how do you symbolise the concept of emptiness/absence?

Any and all suggestions welcome.

2

Dotted outline of the symbol used to mark rows, with a pale shade of grey, or white inside?

3

That same symbol, or a pair of that symbol, with a red “X” through it.

In Microsoft Visual Studio, the icon for “Set Breakpoint” is a hand (left, palm facing, as in signalling someone to stop), and the icon for “Clear All Breakpoints” is two hands (both left, palm facing, as above), one behind the other, with a red “X” superimposed on them.