Mark and Cut the Board with Precision

What happens here

Transport the actual piece of composite deck board that is to be fitted to the miter saw station. Place one end of the deck board firmly against the inside face of one of the deck posts. While holding it steady, use your finger or a pencil to mark the exact point on the board where the inside face of the *other* deck post meets the board. This direct contact marking eliminates any potential inaccuracies from tape measure readings or transfer errors. Once marked, carefully cut the composite deck board using a miter saw at the precisely marked line. This cut should be perfectly square to ensure a flush fit.

Goal: Achieve an exact cut length by marking directly from the installation site.