Snap to Grid
Flash CS3 Tutorial
How to Enable Snap to Grid Feature in Flash
Using the Flash Grid feature you can quickly arrange objects in a grid pattern.
Add a rectangular object to the workspace with the Rectangle tool (r key).
With the rectangle selected, change its size to 100 pixels by 100 pixels in the Properties panel (Cmd/F3 (PC-Ctrl/F3)).
Deselect the object and click the size button in the Properties panel and set the stage Dimensions to 600 pixels by 600 pixels and click OK.
Choose View > Grid > Edit Grid.
Set the grid size to 100 pixels in both directions and click the Show Grid and Snap to Grid checkboxes.
Click OK. Click the rectangle center and drag it to the intersection of two grid lines. It snaps to the grid lines.
Duplicate the rectangle (Edit > Duplicate) multiple times and drag the copies to the other grid line intersections.