### Extending Selections in xterm:
1. **Start the Selection:**
   - Begin by selecting a small portion of text at one end (either the start or the end) of the area you want to select.
 
2. **Scroll to the Other End:**
   - Scroll to the other end of the text you want to include in your selection.
 
3. **Extend the Selection:**
   - Carefully click the right mouse button at the point where you want the selection to end. The selection will instantly extend to include the text from 
your initial selection point to the new point.
 
4. **Repeat if Necessary:**
   - You can repeat this process multiple times to extend the selection further, each time clicking the right mouse button at the new endpoint.
 
### Notes:
- **Precision is Key:** This method requires careful placement of the right mouse button click to ensure the selection extends correctly.
- **Behavior Inside the Selection:** Clicking the right mouse button inside the existing selection can lead to unexpected or less easily controlled results.