SMT TAXIING CROSSES RWY WHEN TOLD TO HOLD SHORT. HAD ALREADY CROSSED HOLD LINE; STOPPED AT FIRST ONE HE SAW.

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I LANDED ON RWY 16 AT PWK ABOUT XB20 CDT; WX VFR; AND RECEIVED CLRNC TO GO TO WHAT I THOUGHT WAS HANGAR 9. I REQUESTED TO GO TO THE YELLOW HANGARS WHICH I FOUND OUT LATER WAS ACTUALLY HANGAR 8. I WAS UNFAMILIAR WITH THE ARPT AND TOLD THE TWR SO; AND THEY GUIDED ME TO THE PLACE I WANTED TO BE. I WAS CLRED DOWN 12R-10L TO ENTER HANGAR 8 RAMP. WHEN I GOT THERE; REALIZING MY ERROR; I REQUESTED CLRNC TO HANGAR 9. I RECEIVED A CLRNC TO HOLD SHORT OF 12L AND R ON YANKEE. BEING ON THE VERY N END OF THE RAMP; WHEN I TURNED AROUND; I APPARENTLY HAD ALREADY CROSSED THE HOLD LINE FOR 12R AND TAXIED TO THE FIRST ONE I SAW WHICH WAS 12L. THE RWYS THERE ARE QUITE NARROW; AND I MISTOOK RWY 12R FOR A TAXIWAY; AND UNWITTINGLY TAXIED ACROSS IT. THE TWR INFORMED ME OF MY ERROR; BUT SAID THERE WAS NO TFC AND GAVE ME CLRNC TO HANGAR 9. I WAS UNFAMILIAR WITH THE ARPT; AND DID NOT HAVE THE ARPT DIAGRAM IN FRONT OF ME. I ASSUMED I KNEW WHERE I WAS; BUT IN REALITY; I DIDN'T; WHICH GOT ME INTO TROUBLE. I HAVE ENOUGH EXPERIENCE TO KNOW BETTER THAN TO DO WHAT I DID; BUT I WAS LATE AND IN A HURRY; WHICH PROBABLY HELPED SET UP THIS SITUATION FOR ERROR.