Drilling a hole for an anchor bolt is a lot easier than pounding a masonry nail, and much less likely to cause spalling. Rotary hammers are versatile, too, so you can use them for more than just drilling masonry. At its heart, the rotary hammer is a powerful drill. Like a standard drill, it has a motor that, through a series of reduction gears, turns a chuck. There are two primary types of drive systems in use for rotary hammers: the slotted drive system (SDS), which is available in SDS or SDS-MAX, and the spline drive. Rotary hammer motors vary quite a bit. SDS hammer motors range from 4 to 8 amps. Besides variations in size, there are a couple of different configurations. At the low and top ends, the motors are in an in-line configuration. Somewhat larger, more powerful tools often feature an L-shaped configuration, with the motor shaft perpendicular to the bit. Like most power tools, rotary hammers come in a wide range of models that vary in capacity, durability, speed, and price. A number of factors should be considered to be sure the hammer you choose will suit your needs, including; the impact energy, the balance of the hammer in your hand, the type of job you are planning on using it for, the handle, safety, and reliability.