1 Hold down the CTRL key while pressing the left mouse button.

2 The cursor will now be a boundary selection cursor. Position it either at the upper left corner or the lower right corner of the rectangular area that completely surrounds all the desired symbols.

3 Drag the cursor diagonally until the desired symbols are completely surrounded.

4 Release the left mouse button.

5 To reposition the starting point of the rectangle, press the right mouse button and left mouse button together while dragging the mouse.