The “stretch” command allows you to accurately lengthen or shorten 3D objects by selecting the cross-sectional plane from which to carry out the expansion.
For example, we may want to lengthen the top of a bathroom vanity that has a built-in sink/wash basin. In this case, we generally want to preserve the existing geometry of the sink/wash basin while extending only the flat part of the vanity top. We can do this using the “stretch” command.
Step-by-step instructions:
1. Right click on the desired object and choose the stretch command. (By right clicking again, you can change the stretch direction, for example, from left/right to front/back).
2. Select the part of the object that you wish to lengthen/shorten.
3. Move the mouse in the desired direction to extend the object.
4. Left click to end the expansion when you reach the desired length.
As an alternative to manually moving the mouse in steps 3 and 4, you can enter a numeric value to specify an exact dimension. A positive numeric value will lengthen the object, while a negative value (with the minus sign), will shorten the object. Once you type the desired number, press the Enter key to end the operation.

The following images illustrate the operations described above.