Sorry about the double entry - not intended. Downloading here seems to be a tad different than with the old system.
Actually - might have been more appropriate in the Technical gallery: The diagonal effect was caused by an error - the paper was placed on the enlarging easel upside down - backing toward the lens. I realized that as backing is white, not the emulsion side gray.
Replaced the paper, correctly, and exposed again. Enough of the first exposure penetrated the base to produce that cross-hatching effect. Fortunate accident. - Ed. S.