Here is an example of a target I use and try to get my pitchers to use.  And I want to thank Terry Shaw from Texas for griping enough at me, that I was forced to put it on my site.  He would listen to my excuses for procrastinating until finally I ran out.
1.  Here is the elastic string types I used.  You can buy the one on the left at a fabric store $0.75, to app. $2.00. The one on the right I buy in a roll for about $20.00.  The gold one is just for fun and glitter.

2.  Cut the length of string into 2 halves.  Then you will be ready to cut these two halves

3.  Now you can fold the 2 lengths so they are about 1/3 the length of the remainder.

Cut the elastic string so you have 4 lengths, with 2 lengths 1/3 the length of the other 2.

4.  Tie a looped knot in all 8 ends.

5.  You should have 4 lengths with loops in the ends.

More pix to follow.
Please be patient.

6.  Now put 2 stakes in the ground or use volley ball stanchions.  on the stantions, go around the pole and put the string through the loop.

7.   Then you can put a pencil or a stick through the string in the loop.

8.  If you are in the back yard just put the loop over the stick.  if you can't slip the loop over use a pencil or a stick.

And then, run the long string through the loops of the short strings and you will have one of the best targets money can buy.

It is also good for young catchers because it gets them used to distractions in front of them.  And the ball won't be deflected by the string, it will just pass right on through straight to the catcher, while giving the pitcher instant feedback.

Advanced pitchers should try to hit the corners, and you can put bells on he string for effect.  While beginners should just get it inside of the strings.  Its good for playing horse or pig.  Many times when playing pig, the catcher will move the mit and the arguments begin.