How to Determine the Type of Letter for Your Sign

Types of Changeable Letters


Changeable Letters are used to display custom messages on special signs. Frequent uses for changeable message boards include: outdoor signs, marquee signs, portable signs, church signs, school signs, sidewalk signs, reader boards, and restaurant signs. They are made with letter tracks or rails to hold letters on the sign. Letters are available in a variety of types and sizes. Changeable letters signs are designed to use a specific type and size of letter. Before ordering changeable letters you need to:


    1. Determine the type of letter your sign requires.


    2. Determine the size of letter your sign requires.

Determining the TYPE of Letter

Changeable letter signs typically use flat plastic letters. Older marquee signs (or new signs built using classic marquee theater architectural design) may use classic 3d or dimensional type slotted letters. For slotted marquee letters, please click here.

There are two basic categories of flat letters:
1) Flexible Plastic Letters 
2)  Rigid Letters

Each type uses a different type of Sign Letter Track for mounting the letters. THEY ARE NOT INTERCHANGEABLE. Buying Flexible Letters for signs that require Rigid Letters is a common mistake when selecting plastic letters.


Flexible Plastic Letters

Flex Letters

Flexible plastic letters are thin, with a thickness between .025 mils to .030 mils depending on manufacture. They can be easily bent from end to with one hand.

Note: 1 mil = 0.001 inches.  (.030 mil plastic letters are about the thickness of a credit card.)

Flexible plastic letters are often known by brand names, such as “Copy-Change Letters,” or “Flex Change Letters.” They are used on portable signs and ground level signs, where the letters can be inserted by hand. Flex letters bend to insert into the grooves of the signs track. The track used for Flex Change Letters is also called "Flex Track" or “Texas Track”.

Flexible letters are not well suited for overhead signs and cannot be used with a sign letter changing pole. For outdoor signs enclosed behind a Plexiglas door, vandal or wind covers can cause flex letters to warp. Rigid Marquee Letters recommended for this application.

Flex Change letters are less expensive than rigid letters, making them a cost effective choice for tight budgets. They are also inexpensive to replace. Flexible plastic letters are often available in the same sizes as Gemini Pronto, Rigid Marquee and Rigid Zip Letters.  However, they should not be used to replace them, as they don’t fit the same way in the track.

 Flexible Plastic Letters BEND to fit into Flex Letter Track, as seen below.

Inserting Flexible Letters into Sign Track



Rigid LettersRigid Plastic Letters


Rigid Plastic Letters are on harder and thicker acrylic plastic panels with a thickness between .060 mils to .080 mils thick (.080 mills is about 1/8th inch). (Compare this to the thickness of 2 to 3 credit cards stacked together.)  Rigid letters are often called by the manufacture’s brand name, including these common brands:  Gemini Pronto Letters, Zip-Change, and Rigid Marquee Letters. Each Rigid Letter brand uses the same type of sign letter track called "Push Up Drop Down Track", making them interchangeable. They can also be used on the same sign. Rigid letters cost more than flexible letters, but offer several advantages.

  • Rigid letters are printed on a high grade acrylic plastic that is very durable, fade resistant and will last for many years.
  • The harder rigid plastic will not blow out of the sign track.
  • Rigid letters can be used with a letter changing pole for elevated signs.
  • Rigid letters can withstand much higher heat then Flex Letters.
  • Rigid Letters are also available in a wide variety of fonts and colors.

 Rigid letters are placed on the sign by pushing the top of the letter under the top track, then pushing the letter flat against the sign, then letting it drop into the bottom track.  

This is why the sign track used to hold rigid letter on a sign is often called “Push Up, Drop Down Track or PUDD”. Depending of the manufacturer, it may also be called “Zip Track,” “Pronto Track,” or “3 Component Track.” 

If your  sign’s letter track looks like the track below, your sign uses Rigid, Pronto or Zip Letters.

Inserting Rigid Letters in Push Up Drop Down Track


How to Determine the Size of Letter your Sign uses


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