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.
However, standard drill bits are generally designed for wood, metal, or masonry, and one can familiarize oneself with different bit types before buying drill bits from a hardware store or an online source like eBay. Additionally, bits designed for metal can usually be used on softer materials like wood or plastic.