The thin white line at the edge is the print shop’s most common “wish they’d asked” error, and the cause is almost always missing bleed. This article explains bleed and trim simply.Three conceptsTrim: the final cut line — e.g. a business card at 85×55 mm.Bleed: the area 3 mm beyond the cut line. Background colour/image extends to here so a slight knife shift doesn’t leave white.Safe zone: 3–5 mm inside the cut line. Text and logos must stay inside so they aren’t cut.Correct measurementsStandard print uses 3 mm bleed and a 3–5 mm inner safe zone. Large format and packaging may use more bleed. Confirm with your printer per job.Setting it in your appIn Illustrator/InDesign, set “Bleed” to 3 mm when creating the document; extend the background to that red line. On export, choose PDF/X and tick “Use Document Bleed Settings.” In packaging it works with the dieline — see our dieline guide.In our experience half of the files that say “I left a little margin, it’ll be fine” show a white line at the cut. Bleed is a 30-second setting; skip it and the whole print is at risk.Quick check3 mm bleed added?Background extends into the bleed?Text/logo in the safe zone?Next stepNot sure your file has bleed? Have it checked before print. Send your file — we’ll run preflight. For full setup, the print file setup guide.Ömer Faruk Ceylandağ · Ceylan Ofset — prepress, Samsun.