I will mark with a Sharpie on the toe and heel of the boot where I want to center of the wheels to line up, this will locate the chassis side to side. With the front/back wheels on the chassis I will set the boot on top of the chassis and balance it against something so the boot/chassis stand on their own. From there I will take 2 similar objects that will allow me to determine space between the end of the wheel and the front of the toe/back of the heel, I like to use empty beer bottles that I just polished off. Place the beer bottles touching the ends of the wheels on both the front and back. Then take a step back and see if the spacing is equa-distant. You can also use a front or back bias if you so choose to suit your skating style. Once the chassis is lined up front to back, make some more markings with a Sharpie to locate the chassis appropriately. Once I have located the chassis to my liking, I will use clear hockey tape to wrap around the boot and chassis to hold it in its proper place. From there I will drill all of my pilot holes in the sole. Once the pilot holes are done, you can remove the chassis and go to the proper bit to fit the hardware. I like to use something slighty oversized to account for any error/making fine tuning adjustments. Hope this helps!!!