The gutter Clear mesh is extremely easy to fit. It has been designed to take into account variations in tile position, different types of tiles (either flat or profile) and also obstructions to the back edge of the gutter (either eaves tray of roofing felt.)

The clip slides over the mesh and grips it and clips onto the gutter securely.
The ideal installation is to slide the mesh underneath the tile and above the felt or eaves tray. The mesh can be fitted below the tile or if the tile is a flat tile it can be fitted on top of the tile.
There are other types of mesh product available but they have inherent problems with fitting for universal applications.
The flat rigid type of mesh product will not fit into the gutter if the tile position is low or if there is an obstruction to the back edge of the gutter (eaves tray , felt etc.)

Because this rigid mesh sits flat on the gutter and just below its top.