If you want to place a lot of blocks at once you run the risk of clicking a lot. With the 'STuFf it' command it's merely a matter of selecting a polyline. The command will fill the polyline with the block you have selected. By default the command will place them randomly but the blocks can also be placed in a neat grid. The command allows you play a around with the spacing so you can decide how dense the block placement should be. With this command it's easy to draw a forest or a field with flowers.