In some engines jack-bolts are used while in some others, waist-ed bolts are used for holding main bearing keep.

To minimize bending tie rods are kept closer to the center line of the shaft, in some type of engines require jack up bolts for keeping bearing keeps in position. In some modern engines twin tie rods are used( so
they will offset to their center line) and are threaded on to the top of the bed plates. This increases the performance of bearings and bearings can be kept on position using waist-ed bolts as they give more compression and they are also resilient.