Christine Andersen Jun 24, 2022:

Possibly placing heavy materials on trestles on the site, to make it easier to lift them - to save workers bending to get them off the ground?
Lifting correctly and avoiding too many heavy lifts is important in health and safety at work.

Diarmuid Kennan (asker) Jun 24, 2022:

Not much context I don't have any useful context, but the phrase appears a few times.
"storage on trestles" would work.

Thomas T. Frost Jun 24, 2022:

Stock, trestles 'Oplag' means 'stock', and 'buk' means 'bracket', 'horse', 'standard', 'trestle', 'pedestal' (ref. L&H Teknisk Ordbog). I guess it means materials must be stored on some kind of trestles when appropriate, but there isn't much context.