A method for producing a glass component, the method comprising: providing an outer cladding tube with a longitudinal axis (x), the outer cladding tube having a first inner bore and a second inner bore separated by a chamfered region (114; 442) having a triangular, polygonal or round shape in cross section, wherein the first inner bore has a height of D 1, and wherein the second inner bore has a height of D 2, each measured perpendicular to the longitudinal axis (x), and each portion of the chamfered region (114; 442) has a height measured perpendicular to the longitudinal axis (x) greater than D 1 and D 2; inserting a spacer (120; 430) into the first inner bore, the spacer (120; 430) having a length measured parallel to the longitudinal axis (x) greater than the height D 2 but less the greatest distance between a deepest point of the bottom of the chamfered region (114; 442) and an intersection of the top of the chamfered region (114; 442) and the first inner bore; inserting a first core rod into the first inner bore; moving the spacer (120; 430) into the chamfered section, thereby causing the spacer (120; 430) to rotate within the chamfered region (114; 442); and rotating the cladding tube into a vertical orientation, whereby the spacer (120; 430) is prevented from entering the second inner bore and the first core rod is supported by the spacer (120; 430), wherein the spacer (120; 430) has a leading edge that is adjacent to the second inner bore when the spacer (120; 430) is rotated into the vertical position, and the leading edge of the spacer (120; 430) is shaped to fit the chamfered region (114; 442). providing an outer cladding tube with a longitudinal axis (x), the outer cladding tube having a first inner bore and a second inner bore separated by a chamfered region (114; 442) having a triangular, polygonal or round shape in cross section, wherein the first inner bore has a height of D 1, and wherein the second inner bore has a height of D 2, each measured perpendicular to the longitudinal axis (x), and each portion of the chamfered region (114; 442) has a height measured perpendicular to the longitudinal axis (x) greater than D 1 and D 2; inserting a spacer (120; 430) into the first inner bore, the spacer (120; 430) having a length measured parallel to the longitudinal axis (x) greater than the height D 2 but less the greatest distance between a deepest point of the bottom of the chamfered region (114; 442) and an intersection of the top of the chamfered region (114; 442) and the first inner bore; inserting a first core rod into the first inner bore; moving the spacer (120; 430) into the chamfered section, thereby causing the spacer (120; 430) to rotate within the chamfered region (114; 442); and rotating the cladding tube into a vertical orientation, whereby the spacer (120; 430) is prevented from entering the second inner bore and the first core rod is supported by the spacer (120; 430), wherein the spacer (120; 430) has a leading edge that is adjacent to the second inner bore when the spacer (120; 430) is rotated into the vertical position, and the leading edge of the spacer (120; 430) is shaped to fit the chamfered region (114; 442).