A B 767-300 FLC IS CONFUSED BY THEIR HOLDING CLRNC TO ROSUN INTXN AND INCORRECTLY USE THE L-HAND HOLDING PATTERN AS DEPICTED FOR DALEY; SAME SITE LOCATION; DIFFERENT STAR; N OF EGCC; FO.

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WHILE FLYING AND CLRED THE DALEY 1 ARR FROM DCS; APCH CTL TOLD US TO HOLD AT ROSUN AS PUBLISHED. LOOKING AT THE ARR; ROSUN WAS NOT FOUND. HOWEVER; CONSULTING THE ILS RWY 24R CHART AND GOING DIRECT VIA FMC; WE WERE ABLE TO VERIFY ROSUN AND DALEY TO BE CO-LOCATED. WE THEN BUILT A HOLDING PATTERN AT DALEY SINCE WE WERE ON THE DALEY 1 ARR; AND HAD NOT BEEN CLRED ANY OTHER ARR; AND DALEY AND ROSUN ARE AT THE SAME POINT IN SPACE. WHILE HOLDING; WITH 4 OTHER ACFT ON TCASII HOLDING AT DALEY/ROSUN; 3 OF THE 4 ACFT WERE IN L-HAND PATTERNS AND 1 WAS IN A R-HAND PATTERN. IT WAS NOT UNTIL OUR LAST TURN IN HOLDING WE REALIZED THE POSSIBILITY OF OUR ERROR. DUE TO FREQ CONGESTION AND RECEIVING VECTORS FOR THE ILS RWY 24R IAP IMMEDIATELY FOLLOWING THE REALIZATION OF A POSSIBLE DEV AND ANY ERROR HAD OCCURRED; VERIFICATION VIA COM WITH ATC WAS NOT POSSIBLE. SUPPLEMENTAL INFO FROM ACN 448214: LOOKING AT THE ARR; ROSUN WAS NOT FOUND; HOWEVER; CONSULTING THE ILS RWY 24R (11-2 PAGE) AND GOING DIRECT VIA FMC TO ROSUN TO BUILD THE HOLDING PATTERN WE WERE ABLE TO DETERMINE AND VERIFY ROSUN AND DALEY WERE CO-LOCATED. WE THEN BUILT A HOLDING PATTERN IN THE FMC USING ROSUN AND THE PUBLISHED HOLDING PATTERN AT DALEY FROM THE DALEY 1 ARR; SINCE WE WERE ON THE DALEY 1 AND HAD NOT BEEN CLRED ANY OTHER ARR. DUE TO FREQ CONGESTION; RECEIVING VECTORS FOR THE ILS RWY 24R IAP IMMEDIATELY FOLLOWING THE REALIZATION OF A POSSIBLE DEV; AND UNCERTAINTY IF ANY ERROR ACTUALLY OR POSSIBLY OCCURRED; VERIFICATION VIA COM WITH MANCHESTER CTL WAS NOT POSSIBLE. I FEEL THE FIX BEING CO-LOCATED (ROSUN/DESIRED INTXN) WITH BOTH INTXNS HAVING PUBLISHED HOLDING PATTERNS; TO BE A BIT CONFUSING. IF ATC IS GOING TO USE ROSUN AND DALEY INTERCHANGEABLY; THEY EITHER NEED TO MAKE THE PUBLISHED HOLDING PATTERNS THE SAME; OR RENAME THE INTXN. WHEN CLRING ACFT TO HOLD AT INTXNS NOT ON A PREVIOUSLY CLRED ARR; ATC NEEDS TO RE-CLR ACFT TO THE FIX AND THE ARR -- IE; 'CLRED TO ROSUN; HOLD AT ROSUN AS PUBLISHED ON THE ROSUN 1 ARR.'