Up/down deflection wheels (Big wheel): This wheel moves the tip of an endoscope up or down. In the endoscopic view, a big wheel down results in the endoscope angulating upwards and vice versa. To further confuse you in the actual 3 Dimension the endoscope is actually bending downwards but due to the way, the optics and the visual image are organized it seems to be in the opposite direction.
Up/down deflection lock: It is the knob with F written on it. To lock your wheel one needs to turn in the opposite direction of the arrow. This allows the endoscopist to lock his wheel in a particular position. This is usually in the setting of endoscopic therapy/ targeted biopsy.