Besides clicking the mouse you can also move it. Normally when you insert blocks you need to do some clicking but with the 'Trail' command you can sweep. Before you start sweeping you can set a width which defines the rang in which blocks can be placed. You can set a minimum distance that should be between the blocks you will place. If you increase the intensity the command will place more blocks. When everything is set you only have to click once and you can start sweeping the mouse. For speed purposes the command will leave a trail of points. When you hit enter the command will stop. By default the command will convert all the points to blocks. By activating the path option you can let the command draw a spline based on your sweeping.