Guitar Scientist: The Most Powerful Guitar Diagrams Editor Online

Tools panel

Using rectangles to highlight portions of a diagram

Draw rectangles
Activate the 'Draw Rectangles' function, click on the fretboard and drag until you like what you see, then click again to add the rectangle to your diagram.

Color
To add rectangles in different colors you need to select a color with the color picker before drawing the rectangle.

Delete a rectangle
Click on the 'eraser' icon next to the rectangle icon, then click on the rectangle you want to remove.

Delete all rectangles
Click on this icon to remove all rectangles from the document

Snap function
The corners of the rectangle will snap on a grid that divides each fret vertically by 4 and horizontally by 2.
This is active by default and lets you precisely place the rectangles on the diagram. You can deactivate the function to freely draw your rectangle.

Resizing

If you resize a fretboard all shapes will automatically adapt proportionally to still select the same frets.

Layers

Shapes, just like the fret markers, belong to a layer. You can put all your shapes on a layer other than where you placed your fret markers to toggle their visibility independently. To place a shape on a specific layer just select the layer before adding your shape. Shapes and fret-markers can coexist on a layer.