Drilling in the forehead of the stick

To drill holes in the face of long objects, we need to mount the drill in a horizontal stand bolted to the table. The object itself, however, e.g.. The bar is placed on a horizontal table made of planks. So that the workpiece does not slide to the sides, screw two half-rounds on the table plane, which will create a prismatic support for him. Now, the accuracy of drilling will be determined by the correct positioning of the table with the bar in relation to the drill axis. Especially vertical alignment accuracy.