Scaling

Scaling is an operation to increase or decrease the size of an object or any of its components. Select the 'Scaling' tool and click on either an edge or surface. You notice that the edge or surface that you have selected has a rectangle or a box drawn around it in dotted lines, with 4 or 8 green points, called handles.
Clicking on any of the green points or handles allows you to scale and manipulate the size of the object. Notice that if you click on any of the green handles, SketchUp highlights it in red and automatically highlights the opposite handle in red as well. This tells you the direction along which your object will be scaled.

A few useful things to know while you scale an object. Clicking on the 'Ctrl' key while you scale an object, ensures that the object scales around its current center.

Holding down the 'Shift' key while you scale an object ensures that the scaling happens uniformly in all directions. If your object is in 3 dimensions then the object will scale uniformly along all 3 axis, where as it will scale uniformly along 2 axis for a 2 dimensional object.

You can also hold down both the 'Ctrl' and the 'Shift' key together, which ensures that the object uniformly scales in all directions along the current center of the object.