SWT Java Tutorial

top: Specifies the attachment of the top of the control.
bottom: Specifies the attachment of the bottom of the control.
left: Specifies the attachment of the left of the control.
right: Specifies the attachment of the right of the control.
A FormAttachment object specifies the attachment of a specific side of a control.
You can attach a side to a position in the parent composite, to the adjacent side of another control, to the opposite side of another control, or centered on another control.