Got more "J" feet than you can handle?

Got more "J" feet than you can handle?
Ordered extra feet or you combined the accessories from two different machines, and found that you have two or more feet marked "J"?

What trickery is this?

What's a beginner to make of this?

If you look real close you notice on each of these feet is a center mark which is normal. Each of these feet have toes.  #1 has a big toe to the right, little toe to the left and a black knob on the left. #2 has two toes with one single slit down the middle. #3 has a big toe to the left and it's solid metal.  These feet are all the same universal multipurpose foot. Why the difference? 

Different foot designers!  

It's just that simple.

Now,  you may wonder what that black knob is for on foot #1?

It's a bump jumper!  It's suppose to help with thick layers of fabric.