I'm just looking for a little help at setting up a grid index for a map book in ArcGIS 10.5. I've used map book frequently in 9.3 but this is my first time in 10.x and it doesn't quite seem as intutive. I'm just wondering if someone might be able to give me a little advice on choosing optimal settings when using the "Use Page Unit and Scale" option, particularly the polygon height and width? I'm trying to create a grid index of geotagged photo locations along a long stretch of Toronto coast line. I'm trying to keep all the map sheets at 1:500 scale and will display them on a 11X17 map.