Epson GT-12000 User Manual page 39

The third, and probably most precise way to use the document
guides is described below. This method also requires tape.
1. Install the pins in the scanner's screw holes through the
document guide's holes. The guide pin screws into the left
hole and the adjust pin screws into the right hole.
2. Lay the grid document guide on the document table with
the document guide holes over the screw holes in the
scanner. Make sure the larger document guide hole is on
the right (when facing the inside of the cover).
Scanner Basics
2-13