Better Windows Programming: Docking

Use dock property for controls to fill a form vertically, horizantally or completely.

If you set a control dock property to left, the control fill the left side of the form with a fixed length you set.

If you set a control dock property to top, the control fill the top side of the form with a fixed hight you set.

If you set a control dock property to fill and there is no control on the form, the control completely covers the form.