600 x 900mm or 800 x 1200mm
Both sizes are available in this range. The smaller frame suits narrow footpaths, doorways and shared frontages where a larger sign would obstruct the walkway or crowd a neighbour. It is also easier to carry in and out several times a day, which matters more than people expect when the job falls to whoever opens up.
The larger frame is read from further away and holds its own on a wide footpath, a forecourt or a site entrance. It also presents more area to the wind, so it suits a more sheltered position. Where the sign will mainly be seen by people already walking past your door, the smaller size is often sufficient; where you need to be noticed from across a road or car park, the larger one may be the better fit.