WDB HELD ON THE WRONG SIDE OF THE HOLD POS LINE CAUSING A CRITICAL GND CONFLICT WITH A LNDG WDB.

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I WAS MAKING A NIGHT APCH TO STL RWY 12R. I WAS CLRED TO LAND PASSING THE OM. SEVERAL ACFT WERE XING THE RWY DOWN FIELD AS WE MADE THE APCH. AS I BEGAN THE FLARE; I SAW (IN AN INSTANT) A 2-ENG WDB ON MY L; VERY CLOSE. HE HAD HIS TAXI LIGHTS ON SO I WAS ALSO ABLE TO SEE WHAT I THOUGHT WAS A 'HOLD SHORT' MARKING JUST IN FRONT OF HIM. JUST THEN WE GOT A L WING UP AND A YAW TO THE L. IT WAS MOMENTARY; AND A NORMAL LNDG WAS MADE. THE FO DID NOT SEE THE OTHER PLANE; HOWEVER; THE SO SAW WHAT I SAW WITH THE EXCEPTION OF THE PAINTED LINE. THE PAINTED LINE CONFUSED ME BECAUSE I WAS UNDER THE IMPRESSION THAT; IN THE UNITED STATES; 'HOLD SHORT' LINES VIOLATED STANDARD RWY MARKINGS. ALSO I HAVE BEEN FLYING OUT OF STL FOR MANY YRS; AND DID NOT REMEMBER SEEING THESE LINES. THE NEXT DAY; WHEN WE WERE DEPARTING STL; WE WERE GIVEN A CLRNC TO 'TAXI VIA ALPHA SOUTH; HOLD SHORT OF RWY 12R ON RWY 24.' WHEN WE WERE CLRED TO CROSS 12R; WE WERE TOLD TO HOLD SHORT OF TXWY P. GRANTED; THE DASHES ARE ON THE OTHER SIDE OF THE SOLID LINE; BUT I THINK THAT THE ACR B PLT MAY HAVE RECEIVED THE SAME CLRNC. IT WAS DARK; AND HE PERHAPS WAS NOT AS FAMILIAR WITH THE ARPT AS WE WHO OPERATE STL AS A HUB. SO WHEN HE WAS TOLD TO 'HOLD SHORT OF PAPA;' HE MAY HAVE ASSUMED THAT THE LINES WERE THE APPROPRIATE HOLD SHORT POINT. FURTHER; THE MARKINGS FOR TXWY PAPA ARE MUCH HARDER TO FIND THAN THIS NEW HOLD SHORT LINE. I SUGGEST BETTER SIGNAGE FOR TXWY PAPA. ALSO; I BELIEVE GND CTL SHOULD MODIFY THEIR PHRASEOLOGY SO THAT PLTS XING RWY 12R ARE TOLD TO IGNORE THE PAINTED LINE. DUE TO HVY TFC ON THE GND AT THE TIME; CTLRS HAD NO WAY OF KNOWING THAT ACR WAS FOULING THE RWY. THIS WAS A CLOSE ONE. BY THE WAY; WE HAVE A PROB AT STL HOLDING SHORT OF RWY 12R ON RWY 4. THERE ARE NO MARKINGS OR SIGNS FOR HOLDING SHORT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR SAID ACR B WDB WAS HOLDING ON RWY 6; N OF RWY 12R AND ON THE S SIDE OF THE HOLDING POS LINE. HE SHOULD HAVE BEEN ON THE N SIDE OF THAT LINE. RPTR ADDED THAT; IF HE HAD LANDED WELL TO THE L ON RWY 12R; HIS WING WOULD SURELY HAVE HIT THE TAIL OF THE HOLDING WDB. HE ADDED THAT THE JET BLAST FROM THE HOLDING ACFT WAS 'NO BIG DEAL.' IN ANOTHER CALLBACK WITH ATC AT STL; ANALYST FOUND THAT THEY HAVE HAD PROBS IN THE PAST WITH PLTS MISINTERPRETING THE HOLDING LINE AND HOLDING ON THE WRONG SIDE OF THE WRONG LINE.