Measure the length of each bar counter edge with a tape measure. You will need to take measurements for each edge where you will install the bar rail.
Set the bar rail on two or more sawhorses. Evenly space the sawhorses beneath the bar rail.
Transfer your length measurements to the bar rail. Use a speed square to make a straight line.
Cut wood bar rails using a handsaw; a jigsaw is an electric tool that will make faster cuts. Use a hacksaw or disc grinder to cut metal bar rails.
Sand the cut edge with sandpaper to smooth it out.
Dry fit the bar rail in its place to ensure it fits. Repeat step 4 to cut the bar rail again to make it fit in place.