die  block  that  has  holes  for  3/16-,  1/4-,  5/16-,  3/8-, 7/16-, and 1/2-inch O.D. tubing, and a clamp to lock the tube in the die block. It also has a yoke that slips over the die block and has a compressor screw and a cone that forms a 45-degree flare or a bell shape on the  end  of  the  tube.  The  screw  has  a  T-handle.  A double flaring tool has the additional feature of adapt- ers that turn in the edge of the tube before a regular 45-degree  double  flare  is  made.  It  consists  of  a  die block with holes for 3/16-, 1/4-, 5/16-, 3/8-, and 1/2- inch tubing, a yoke with a screw and a flaring cone, plus  five  adapters  for  different  size  tubing,  all  carried in a metal case. CARE OF HAND TOOLS Tools are expensive, vital equipment. When the need for their use arises, common sense plus a little preventive  maintenance  prolongs  their  usefulness. The  following  precautions  for  the  care  of  tools  should be observed: 1.  Clean  tools  after  each  use.  Oily,  dirty,  and greasy tools are slippery and dangerous. 2.  NEVER hammer with a wrench. 3.  NEVER leave tools scattered about. When not in use, stow them neatly on racks or in toolboxes. 4.  Apply a light film of oil after cleaning to prevent rust  on  tools. 5. Inventory tools after use to prevent loss. TACKLE A tackle is an assembly of blocks and ropes used to gain a mechanical advantage in lifting or pulling. Figure 2-18 shows the name and location of various main parts of a tackle. In working with tackle, it helps you to understand the meaning of a few simple terms you hear used. The term fall means  a  rope,  either  manila  or  wire,  reeved through a pair of blocks to form a tackle. The hauling part is the part of the fall leading from one of the blocks upon which the power is exerted. The standing part is the  end  of  the  fall  of  the  blocks.  The  movable  (or running) block of a tackle is the block attached to the object to be moved. The fixed (or standing) block is the block attached to a fixed object or support. When a tackle is being used, the movable block moves up and down and the fixed block remains stationary. The mechanical  advantage  of a tackle is the term applied to the relationship between the load being lifted and the power required to lift that load. Thus, if a load Figure  2-18.—Parts  of  a  tackle. of 10 pounds requires 10 pounds of power to lift it, the mechanical advantage is 1. However, if a load of 50 pounds requires only 10 pounds to lift it, then you have a mechanical advantage of 5 to 1, or 5 units of weight are lifted for each unit of power applied. The easiest way to determine the mechanical advan- tage of a tackle is by counting the number of parts of the falls at the movable (or running) block. If there are two  parts,  the  mechanical  advantage  is  two  times  the power applied (less friction). A gun tackle, for instance, has a mechanical advantage of 2. Thus, to lift a 200- pound load with a gun tackle requires 100 pounds of power,  disregarding  friction. By inverting any tackle, a mechanical advantage of 1 is always gained because the number of parts at the movable  block  is  increased.  By  inverting  a  gun  tackle (fig. 2-19) a mechanical advantage of 3 is attained. When a tackle is inverted, the direction of pull is diffi- cult. This can be easily overcome by adding a snatch block, which changes the direction of pull, but does not increase  the  mechanical  advantage. 2-12