This page will explain what a concatenated message is and how it works on the sidekick iD
If you wish to compose a message that exceeds the maximum number of characters per message (approximately 160), you can do so simply by continuing to type past the maximum number. You'll know when you've crossed the limit by looking at the message count indicator below the message or at the Compose screen title bar. In the example shown below, the message has grown to the equivalent of two messages. When you send a long message, the message is broken into "parts", which are then concatenated (linked together) when the message is received. You can compose up to the equivalent of 20 messages. Note that your wireless operator may charge you for the equivalent number of messages.

Back to Compose Text Message screen.