you can make a rail fence block almost any size you want...just make sure that the size of the finished block can be divided by three in a way that you can find the measurement on a quilters ruler. For example, two posters wrote about the 6 inch and 4 1/2 finished sizes...you can make it 12 inch finished if you want...Once you decide on the finished size of the block, divide that number by three to get the finished size of each strip...then to cut the strips, add one half inch for seam allowances.