Decide on a layout for the wall ledges. For example, you can lay the ledges out in a horizontal row or a vertical column. Ask an assistant or two to hold the ledges up to the wall to help you determine the layout.
Consider the elements that you are going to display on the ledges, as you'll want to install the ledges so that there is enough space to display the items. This is particularly important if you are hanging the ledges above one another. It may be helpful to measure the tallest items that you want to display in order to ensure adequate space for them.
Space out the ledges. Once you've determined the layout and the items you want to display on the ledges, ask an assistant or two to hold the ledges on the wall, arranging them so that there is enough space between them to accommodate the display items and create a visually appealing look. If you've measured the items you want to place on the shelves, incorporate the measurements when spacing out the ledges.