when square a surface in alias, why i can't select curves, but points?

[Anonymous]

when square a surface in alias, why i can't pick curves, but points to construction a surface?

but when I press ctrl & alt buttons, then can pick curves, it's curiously.

why?

[duaxiong]

In the upper right corner of Alias, there is a small button to turn on Curve Snapping...turn it off.