I dont understand that some times i can manipulate the pad by using compass in part design
it just asks that do you want to make the sketch free
but sometimes it shows a message that some elements are fixed
why it is so
i mean how would i get to know that which features i can manipulate using compass
I think when you draw a sketch,
you completely constrain it which means your sketch has a fixed position related to axes (like XY).
so in order to move the pad, try not to give dimensions related to axes.