You don't have to leave one side out to do this.

If your pistons are setup for double locks all you have to do is leave one out. The pin will beat back and forth until it kicks the other one out.

I sent a piston and rod to the machine shop for bob weight measuring. They left one lock out. If it had not been for the ring rail the pin would have hit the cylinder wall. I had the engine apart for something else and caught the problem before really tearing a lot of parts up.

Leon