Picture of How to Miter a Panel
Mitering the edges of two panels that but up against each other is the best way to create a stone facade appear seamless. 
Here's a quick tutorial on how to cut corners that you can be proud of!

To miter a panel on your own you will need:
Measuring tape
A Power Drill
Caulk (preferably a color that will blend with your panel)
ATable Saw or Circular Saw
A File
Touch-up Paint

Step 1:

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Measure and mark the end of your panel. Remember to measure twice, maybe three times, and cut once.