A combustor of a gas turbine engine including a combustor shell having an interior surface, a first panel mounted to the interior surface at a first position and a second panel mounted to the interior surface at a second position. The first panel has a first end, a first combustion chamber surface parallel with the interior surface, a first rail extending from the first combustion chamber surface toward the interior surface of the combustor shell, and a first extension extending axially from the first rail to the end of the first panel. The second panel has a second end, a second combustion chamber surface, and a second rail extending from the second combustion chamber surface toward the interior surface of the combustor shell. The first end and the second end are proximal to each other and define a circumferentially extending gap there between.