both convenient and fast for the modern bartender. It is advantageous in that it is easy to open several bottles in rapid succession, and with more flair than other types of bottle opener. Consequently, 'bar blading' is often part of bar flair routines. Wall-mounted Works the same as the lever variation, except that it is attached to the wall, to allow for simpler bottle-opening, which can be done with one hand. The bottle cap can fall into a bottle cap catcher mounted below the opener, or it can be retrieved after removal from the bottle. A variant to this are similar types of openers mounted on older vending machines. Multi-opener Also known as a beverage opener, these usually includes a bottle opener of the simple bottle opener style but includes various other openers such as for plastic bottles or metal beverage cans. Technique Under most use, a bottle opener functions as a second-class lever: the fulcrum is the far end of the bottle opener, placed on the top of the crown, with the output at the near end of the bottle opener, on the crown edge, between the fulcrum and the hand: in these cases, one pushes up on the lever. However, one may instead use it as a first-class lever, by placing the near end on the top of the crown, and the far end under the crown edge, then pushing down on the lever (thus the output is on the opposite side of the fulcrum from the hand). This is particularly used with bar blades, which form an obtuse angle. Mechanically, this is a marginally less effective lever, as the effort arm is shorter, but the action of pushing down is marginally anatomically easier. While most lever-type bottle openers can be used in either configuration, the designed use can be determined if one of the edges is curved, in which case this edge is designed to sit in the middle of the crown, as the curve concentrates pressure, deforming the crown, and a curved edge does not connect with as much of the crown edge, hence being suboptimal and slipping more frequently if used to connect with the crown edge. This difference can be seen in comparing the traditional opener and contemporary bar blade at right. Corkscrews Waiter's friend The 'waiter's friend' or 'wine key' consists of a flat housing (often plastic covered) similar to a Swiss army