Museum Classroom: Flag Semaphore

Lesson: Flag Semaphore
Topic: The exploration of types of nautical communication
Grade: 1-8

Activity: Flag Semaphore Flash Cards

Materials Required:

  • Pencil
  • Eraser

Materials Provided:

  • Flag Semaphore Flash Cards
  • Flag Semaphore Decoding Key

Pre-Lesson: Discussion of Communication
Task students to order themselves based on birthday or height. They cannot speak to each other in order to communicate. Once students complete the task, discuss strategies they used in order to communicate. What worked best? What was the biggest challenge? How do we use non-verbal communication every day? How do we know what another person is trying to communicate based on gestures, hand-signs or body language?

Ships on the Welland Canal have a way of communicating without speaking as well. They use internationally recognized flags. Each flag represents a number or letter.  Another ship can communicate important messages to ships around them by waving semaphore flags in a certain position. Semaphore flags were often used in the 19th century, however the flags are still used to communicate today, especially during underway replenishment (transferring fuel, munitions, and stores from one ship to another while underway), at night, or in an emergency. 

This activity will work best with a partner or small group. Print the Flag Semaphore Decoding Key (you may need to make multiple copies).

Note: : if you do not have access to a printer, STCM recommend the following to complete the activity:
1. Download the Flag Semaphore Decoding Key and keep open on preferred electronic device (i.e. computer, laptop, iPad, tablet, etc.). If you have multiple devices, we recommend downloading the Flag Semaphore Decoding Key on each device and providing each partner or group with a copy.

Once you have downloaded your decoding key, make two copies of Flags Semaphore by either taking 2 blank pieces of paper and colouring one diagonal side of the paper red and the other yellow or using red or yellow construction paper instead. Review the Flag Semaphore Decoding Key if you need assistance on how the flag should look. The flags will always remain the same, however it is the position of the flags that change the letter.

After each partner/group has completed making a set of Flags Semaphore, as a warm up and all together go through the different Flag Semaphore movements for each letter a couple times using the decoding key. This will help with understanding each letter code.

Select one person to choose a variety of maritime words to write down on post-it note sized pieces of paper. Put the words into a bowl or jar. Each partner or group will have an opportunity to draw a word. One partner or group member begins, choosing one member from their team to stand in front of the other partner/group with the Flags Semaphore. The partner or group member is given a maritime related word to spell out to the other partner or group with the flags using the correct Semaphore positions. Each team works together to decode the word, and find the definition in the dictionary. You can use a physical copy or an online dictionary. The first group to find the correct word and definition wins the round. If the team of the individual using the flags wins, the team earns two points. If another team get the point, one point is earned. Choose a new group for each round. If possible, every individual should be able to participate at least once with the Flags Semaphore. At the end of the game, the team with the most points wins.

Wrap-up Discussion
As a group altogether, discuss the challenges each group found in communicating their message. What challenges did the audience have in understanding the code? What are the benefits of using non-verbal communication on a ship? Could we use the Flags Semaphore/positions in our daily life at school? When might it be beneficial to use Flags Semaphore/positions at school?

Extension Activity
Write a journal entry on your experience using non-verbal communication and the benefits and challenges they encountered.


All partners or groups take a picture and post it to social media (i.e. Instagram, Facebook, Twitter, etc.). Before posting the picture, select one person to come up with a caption however, they have to share the caption with the group using the Flags Semaphore while the others use the decoding key to figure out the caption. Tag @stcmuseum to show us your best Flag Semaphore poses!

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