The following is a study of the Air Force regulations concerning ribbons. Most of the regulations are straight forward, but there are some exceptions that can be left up to interpretation.
No choice of spacing.
There is no space between the rows of ribbons.
Wear your ribbon rack three or four ribbons wide.
4 thru 9: multiples of 3 or 4, centering any remaining ribbons on the top row.
Staggered right configuration is not allowed unless over 10 ribbons have been earned.
10 or more: multiples of 3 or 4 in at least the 2 bottom rows; but to prevent coat lapel from covering ribbons, each additional row may contain less than 3 or 4 or less, with top row centered over the row immediately below.
You may choose to center or stagger the ribbons to the right. If you choose standard ribbons you will not have a choice of four wide due to manufacturing limitations. If thin ribbons are selected you can choose from any configuration you like.
No more than four devices per medal.
Wear a maximum of four devices on each ribbon.
Silver claims higher precedence than bronze.
Place silver devices to the wearer's right of bronze devices.
Wear a second ribbon for over four devices
If all authorized devices do not fit on a single ribbon, wear a second ribbon. Wear a minimum of 3 devices on the first ribbon before wearing a second ribbon.
The arrowhead claims precedence over other devices.
Point the arrowhead up in a vertical position to the wearer’s right of all service stars.
The V device claims precedence over other devices.
When worn with oak leaf clusters, place the "V" devices to the wearer's right of the clusters.
Use regular size devices.
Wear regular devices on regular medals and regular ribbons; miniature devices on miniature ribbons and medals. Wear all the same size devices.
Wear medals earned from other services as their regulations read.
Wear ribbons awarded by other Services with appropriate device that Service authorized.
Below is a picture of device configurations on ribbons taken from the regulations.
As for the rack builder we interpret the regulations concerning ribbons as follows: