The current study aimed to evaluate the influence of rectangular obstacles with different aspect ratios on the skin friction coefficient of a flat plate in a turbulent boundary layer, using experiments in a suction-type wind tunnel with the floating-element technique. Obstacles having rectangular shapes with various c/t ratios of 2, 4, 8, and 18 were placed within the turbulent boundary layer at a distance of 2 mm from the flat plate surface. Four distinct values of Reynolds numbers at various free-stream velocities of 10, 11, 12, and 14 m/s were used for testing purposes. First, the experimental system was verified by comparing the skin-friction coefficients for a smooth flat plate with those obtained from an analytical correlation of the turbulent boundary-layer flow. The validation study results indicated excellent agreement between the experimental data and the analytical solutions. It was observed that mounting rectangular obstacles had a substantial effect on reducing the skin friction coefficient compared to the case without obstacles. The smallest value of the skin-friction coefficient was obtained for the obstacle with an aspect ratio c/t = 2.Moreover, as the Reynolds number increased, the skin friction coefficient decreased. The results above confirm that the mutual interaction between the generated vortices and the turbulent boundary layer modifies the flow characteristics, resulting in lower wall shear stress. This study shows that appropriately shaped rectangular obstacles can reduce turbulent skin friction drag, which may help reduce drag.