Tonsils usually sit at or above the dashed line (a few millimeters below can be normal). The fluid space behind them is open.
Tonsils extend below the line (blue bracket) and often crowd the space where fluid should pass. Red marks show where flow is often restricted.
Arrow keys turn the model. Shift and arrow keys move it. Plus and minus zoom. Press 1 for side, 2 for back, 3 for below, 4 for front, and 0 to reset.