What is the most frequently used nonprojection-type teaching aid?

The marker board is the most frequently used nonprojection-type teaching aid because it offers versatility and immediate engagement in a learning environment. Instructors can quickly draw diagrams, write down key points, or illustrate concepts in real-time, making it an interactive tool that encourages participation from students. Its ability to be easily modified during a lesson allows for the flexibility to adapt to different teaching moments and clarify concepts as questions arise, enhancing the overall learning experience. The simplicity and accessibility of the marker board make it a staple in various educational settings, particularly in fire rescue training where dynamic explanations and quick visual representations are essential for understanding complex principles.