Tactical symbols, primarily intended for British armour 1944-45, but useful for all manner of forces. These are in yellow, which was normally used by the second regiment of an armoured brigade. Note that the smaller squares are intended to be positioned on their corners (ie. as diamonds), this being the normal marking for regimental HQ vehicles.
These markings, rather than just plain yellow, have a very fine (1/600"....) black edging to them. This is an aesthetic rather than a historical choice; it helps the marking to stand out, especially on camouflaged models.