When you first open the Screen Designer, the Selector is highlighted in the Screen Component Toolbox and the mouse pointer is a white arrow.

When you select any control in the Toolbox and move the mouse to the screen form, the mouse pointer becomes a crosshairs. After you draw a control on the screen, the mouse pointer returns to being an arrow, and the Selector icon appears highlighted in the Toolbox. When the Selector is chosen, you can select, move, and resize controls already drawn on the screen form.

If you have selected a control type in the Screen Component Toolbox and decide that you don't want to draw that control on your screen, you can cancel your selection by clicking the Selector icon.