Design Guidelines (VCL Only)
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When you are arranging components on a form, design guidelines appear on the Form Designer on or near a component's bound. Design guidelines are vertical or horizontal lines that cut across the bounds of a visual control (top, bottom, right, left, center, and text guidelines). You can use the design guidelines as "alignment" points to align adjacent controls.
When you mouse-over a control, a popup window displays UI guideline information, so that you can see how each component will adhere to rules, such as position of origin (horizontal, vertical), size of the selected control, tab stop, and relative order of an item (in groups, listboxes, or menus).
If the Snap to Grid option is enabled, and Use Design Guidelines is also enabled, the design guidelines will take precedence. This means that if a grid point is within the tolerance of the new location and a guideline is also within that distance away, then the control will snap to the guideline instead of the grid position, even if the guideline does not fall on the grid position. The snap tolerance is determined by the grid size. Even if the Snap to Grid and Show Grid options are disabled, the Designer still uses the grid size in determining the tolerance.
To enable or disable design guidelines, set the Use designer guidelines field on the Tools > Options > Environment Options > Form Designer dialog box. The design guidelines feature is available only in VCL applications (for both Delphi and C++).
For more information, see Using Design Guidelines with VCL Components.