Wegener also noted that the continents move up and down to maintain equilibrium in a process called isostasy. As an example he cited the sinking of Northern Hemisphere lands under the weight of continental ice sheets in the last ice age, and their rise since the ice melted some 10,000 years ago.
Drill bits are cutting tools used to create cylindrical holes, almost always of circular cross-section. Drill bits come in many sizes and have many uses. Bits are usually connected to a mechanism, often simply referred to as a drill, which rotates them and provides torque and axial force to create the hole.
Hammer drills often have a selection switch which allows users to choose between rotary and rotary-plus-hammer modes. When used in rotary mode, a hammer drill can be used for all of the drilling and driving applications that an ordinary drill driver is used for. In rotary-plus-hammer mode, the drill is set to be used on masonry. So when set properly, a hammer drill can almost always bore the hole. If the project requires drilling in masonry, you're going to need the hammer function.