While editing...

while editing some pipes in model made by bhairav unknowingly i deleted one little surface but after doing some editing in the model i resaved that file than i looked once i found that i deleted one surface so now i have to make it again for that i tried shift+F method but i didnt get the surface way i wanted than i did it with exrude and grab method than coinciding each vertex and than remove by pressing W and REMOVE DOUBLES method but it is very much time consuming so people if u find some other and better way than please let me know...

and to make anything spherical or a set of vertices forming a loop into circle shape there is tool called TO SPHERE is available for that we need to select the loop of vertices after that make the CURSOR->SELECTION by doing this 3d cursor will come at the center of the selected loop of vertices and after that press TO SPHERE tool in MESH TOOLS...it will form a circular shape and the 3d cursor will act as a center for that circle..

Nitin