SQUARE files are tapered on all four sides and are used to enlarge rectangular-shaped holes and slots. ROUND files serve the same purpose for round openings.  Small  round  files  are  often  called  “rattail” tiles. The  HALF  ROUND  file  is  a  general-purpose  tool. The rounded side is used for curved surfaces, and the flat face on flat surfaces. When you file an inside curve, use a round or half-round file whose curve most  nearly  matches  the  curve  of  the  work. Kits  of  small  files,  often  called  “swiss  pattern”  or “jewelers’” files, are used to fit parts of delicate mechanisms  and  for  filing  work  on  instruments. Handle  these  small  files  carefully  because  they  break easily. Filing  Operations Using  a  file  is  an  operation  that  is  nearly indispensable  when  working  with  metal.  You  may  be crossfiling, drawfiling, using a file card, or even polishing  metal.  Let’s  examine  these  operations. When you have finished using a file, it may be necessary  to  use  an  abrasive  cloth  or  paper  to  finish the  product.  Whether  this  is  necessary  depends  on how fine a finish you want on the work. CROSSFILING.  –Figure 1-30, view A, shows a piece of mild steel being crossfiled. This means that the tile is being moved across the surface of the work in  approximately  a  crosswise  direction. For  best results, keep your feet spread apart to steady yourself as  you  file  with  slow,  full-length,  steady  strokes.  The file cuts as you push it – ease up on the return stroke to keep from dulling the teeth. Keep your file clean. View B shows the alternate positions of the file when  an  exceptionally  flat  surface  is  required.  Using either  position  first,  file  across  the  entire  length  of  the stock. Then, using the other position, file across the entire  length  of  the  stock  again.  Because  the  teeth  of the file pass over the surface of the stock from two directions,  the  high  spots  and  low  spots  will  readily  be visible after filing in both positions. Continue filing first in one position or direction and then the other until the surface has been filed flat. Test the flatness with a straightedge or with prussian blue and a surface plate. DRAWFILING. –Drawfiling produces a finer surface  finish  and  usually  a  flatter  surface  than crossfiling. Small parts, as shown in view C, are best held in a vise. Hold the file as shown in the figure; notice  that  the  arrow  indicates  that  the  cutting  stroke is away from you when the handle of the file is held in  the  right  hand. If the handle is held in the left hand,  the  cutting  stroke  will  be  toward  you.  Lift  the file  away  from  the  surface  of  the  work  on  the  return stroke. When drawfiling will no longer improve the surface texture, wrap a piece of abrasive cloth around the file and polish the surface as shown in figure 1-31, view A. USE OF FILE CARD.  — As you file, the teeth of the file may “clog up” with some of the metal filings and  scratch  your  work.    This condition is known as PINNING. You can prevent pinning by keeping the file teeth clean. Rubbing chalk between the teeth will help prevent pinning, too, but the best method is to clean the file frequently with a FILE CARD or brush. A file card (fig. 1-32) has fine wire bristles. Brush with a pulling motion, holding the card parallel to the rows  of  teeth. Always  keep  the  file  clean,  whether  you’re  filing mild  steel  or  other  metals.  Use  chalk  liberally  when filing  nonferrous  metals. FILING ROUND-METAL STOCK.  –Figure 1-30,  view  D,  shows  that  as  a  file  is  passed  over  the surface of round work, its angle with the work is changed. This results in a rocking motion of the file as it passes over the work. This  rocking  motion permits  all  the  teeth  on  the  tile  to  make  contact  and cut as they pass over the work’s surface, thus tending to  keep  the  file  much  cleaner  and  thereby  doing  better work. P O L I S H I N G    A    F L A T - M E T A L SURFACE. –When polishing  a  flat  metal  surface,  first draw tile the surface as shown in figure 1-30, view C. Then, when the best possible drawfiled surface has been obtained, proceed with abrasive cloth, often called emery cloth. Select a grade of cloth suited to the  drawfiling.  If  the  drawfiling  was  well  done,  only a  tine  cloth  will  be  needed  to  do  the  polishing. If your cloth is in a roll and if the job you are polishing is the size that would be held in a vise, tear off a 6- or 8-inch length of the 1- or 2-inch width. If 1-19