A heat shield panel for use in a gas turbine engine combustor, comprising: a base; a hot side; a cold side spaced from the hot side; one or more dilution apertures (314, 414); and a rail disposed about a periphery of the cold side, the rail including a plurality of rail members, including a first axial rail member (304, 404), a second axial rail member (306, 406), a first circumferential rail member (308, 408), and a second circumferential rail member (310, 410), the first circumferential rail member (308, 408) having a first length extending along an axial length (328, 428) of the base, running from the first axial rail member (304, 404) to the second axial rail member (306, 406), a first height extending from the cold side, and a first circumferential rail thickness (350, 450) that varies along the first length, and the second circumferential rail member (310, 410) having a second length the axial length (328, 428) of the base, running from the first axial rail member (304, 404) to the second axial rail member (306, 406) and a second circumferential thickness (352, 452) that varies along the second length; wherein the first circumferential rail member (308, 408) extends in a first direction along the first length and wherein the first circumferential rail thickness (350, 450) varies in a second direction, orthogonal to the first direction, along the first length; wherein the first circumferential rail member (308, 408) varies from a first circumferential thickness, located proximate the intersection of the first circumferential rail member and the first axial rail member, to a second circumferential thickness, located intermediate the axial length, and the first circumferential rail member varies from a third circumferential thickness, located proximate the intersection of the first circumferential rail member and the second axial rail member, to a fourth circumferential thickness, located intermediate the axial length, and characterised in that: the locations of the second circumferential thickness and the fourth circumferential thickness each merge into a boss member that defines one of the one or more dilution apertures, with the boss member being located intermediate the axial length. a base; a hot side; a cold side spaced from the hot side; one or more dilution apertures (314, 414); and a rail disposed about a periphery of the cold side, the rail including a plurality of rail members, including a first axial rail member (304, 404), a second axial rail member (306, 406), a first circumferential rail member (308, 408), and a second circumferential rail member (310, 410), the first circumferential rail member (308, 408) having a first length extending along an axial length (328, 428) of the base, running from the first axial rail member (304, 404) to the second axial rail member (306, 406), a first height extending from the cold side, and a first circumferential rail thickness (350, 450) that varies along the first length, and the second circumferential rail member (310, 410) having a second length the axial length (328, 428) of the base, running from the first axial rail member (304, 404) to the second axial rail member (306, 406) and a second circumferential thickness (352, 452) that varies along the second length; wherein the first circumferential rail member (308, 408) extends in a first direction along the first length and wherein the first circumferential rail thickness (350, 450) varies in a second direction, orthogonal to the first direction, along the first length; wherein the first circumferential rail member (308, 408) varies from a first circumferential thickness, located proximate the intersection of the first circumferential rail member and the first axial rail member, to a second circumferential thickness, located intermediate the axial length, and the first circumferential rail member varies from a third circumferential thickness, located proximate the intersection of the first circumferential rail member and the second axial rail member, to a fourth circumferential thickness, located intermediate the axial length, and characterised in that: the locations of the second circumferential thickness and the fourth circumferential thickness each merge into a boss member that defines one of the one or more dilution apertures, with the boss member being located intermediate the axial length.