This block:
1. allows the user to "stretch" to the desired number of holes in the vertical direction
2. allows the user to stretch the horizontal distance of the holes closest to the opening - this also stretches the shelf
3. allows the user to move the shelf up and down
4. tells the user how many rows of holes there are
5. tells the user how long the shelf is
The three lines on the bottom represent the inside profile of the cabinet box and will not plot.