...Using a 'Transfer Punch', 1/4" Clearance hole. Starting at the First Louver and transferring to the next size up...'A' was the first and Only one Measured, then transferred to B, B to C, C to D...on up to the Last Slat, G. One is Laid over the Next Largest, Centered Perfectly and Aligned Parallele, Exact! Then the Bores Positions are Transferred.
What this does is: Guarantees! Proper orientation, All Slats to Align Perfectly upon mounting. Eliminates any chance of Error with Additional Measurements. All Drilled Holes Exactly Positioned the Same! With the top slat lowered, you can see the Punch Mark on the Next Slat. Then I give it a Heavier/Deeper Blow with a 'Center Punch' and drill it 1/4". Last, 'That' Louver is Transferred to the Next, and up to 'G'.