Creating a gallery wall requires careful measuring. DIY Steps: 1. With a pencil and a level, draw a line across the wall where you want the bottom of the grid. 2. Use a tape measure to mark the width of each frame along that line, adding an equal amount of space between each frame. 3. Using the line as a guide, hang the bottom row with nails. 4. Holding the level vertical, mark a line up from the row below it to determine where your next row will go; repeat.