Using this block diagram maker, development teams can quickly come to a shared understanding of complex systems. Use this free block diagram maker to get started immediately and get everyone in the same direction. Determine your starting point before you begin drawing. Choose the UML forms standing in for your system blocks, and sketch your rough block diagram. Find the interrelationships, and draw the connecting lines. Drag and drop any images you want to use as icons into the interface. Adjust the block diagram's dimensions so that it fits your presentation board's frame.