Tired of carrying the Franklin book or 1000 Piping intersections, then this app for 90 degree pipe intersections, or fish mouth is the answer. For Standard Weight pipe sizes thru 24 simply enter the branch line in the first box and the main line in the second box and press calculate.The results are the ordinates (See Fig 20) for 16 points to lay out a 90 degree intersection. This app assumes youre a journeyman pipefitter (steamfitter) and know how to layout the pipe when the calculated ordinates are given. If not see our webpage http://watersmechanical.com/appsforpipefitting.html for more info. Look for our upcoming app that allows for more pipe sizes and varying lateral degrees.