Mark Info

Standard Mesh Grids
 rm g150 ss  rm normal r

Rim Mark

An Asymmetrical mark in the rim allows for precise orientation of the grid, and aids in the identification of each side.

Centre Mark
More recent grids have an asymmetrical centre marking, enabling the four quadrants of the grid to be distinguished. 
Older grids have a 'reverse arrow' centre marking, enabling each half of the grid to be distinguished.

Note that the central hole is for manufacturing purposes only, and may not appear in the actual grid.

Fine Mesh Grids

 rm g1000hs ss  rm fine r (1)

Rim Mark

An Asymmetrical mark in the rim similar to that found in the standard mesh grids.

Centre Mark
Only some of the 'HH' series of fine hexagonal mesh grids have this centre marking. It effectively divides the grid into six distinguishable areas.

Rim Tab
The older HS and HH grids also have a circular tab on the rim to aid in handling the grid with tweezers. 

Note that no grid has all of the above three features together, the diagram is for illustrative purposes.