Aaeon SBC-555 Manual page 29

Note that the modules can only fit into a socket one way.
1. Insert the memory module into the socket at a moderate angle.
2. Push the module toward the vertical posts at both ends of the
socket until the module is upright and the retaining clips at
both ends of the module click into place. When positioned
correctly, the pins on top of the vertical posts should corre-
spond to the circular holes on the ends of the module.
3. Repeat steps 1 and 2 for each module you install.
If you need to remove a SIMM, follow the procedures below:
1. Supporting the SIMM with a finger, use a pen or a similarly
shaped object and press one retaining clip straight down.
2. Repeat for the other side. When released, the retaining clips
will push the SIMM up and out of its upright position.
3. Carefully pull the SIMM out of the socket with your fingers.
4. Repeat the above steps for each module you remove.