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 that is fitted with a Pipe provides effective connection to the rig surface equipment or application with the bit and the bottom hole assembly for the purpose of pumping the Drill fluid to the bit.
These are used for drilling a range of sizes of hole and they are very useful especially if machine drills are not available. The hand drill generally holds drill sizes from 1mm to 9mm whilst the brace will hold larger drill bits called forstner bits and auger bits. These larger bits can be used to drill blind holes (holes that do not go the entire way through material).