Square Edge 
The edge of the tile simply has a 90 degree cut edge, often referred to as a Board edge. These tiles are usually designed for a 24mm grid but can sit in the 15mm grid too.

Tegular Edge
Tegular edge ceiling tiles are associated with a rebated or bevelled edge to the tile which allows it to sink just below the grid level once installed. It is purely a design feature. Tegular ceiling tiles are usually associated with a 24mm grid. The name ‘Tegular’ can sometimes be used to describe the step edge so check your grid width to be safe.

Microlook Edge
Similar to Tegular Edge, Microlook (or T15/Tegular 15) ceiling tiles, have a rebated or bevelled edge to the tile. The main difference is the fact that the tile is designed to fit in a 15mm grid. Please check grid width to be safe.