A UI element referring to a descriptor for a type of keyframe, known as discrete keyframe, that does not interpolate to its own value from the value of the keyframe before it (as most keyframes do). A keyframe exists at a keytime. Clicking Hold In causes the keyframe to maintain (or hold), until its own keytime, the value of the keyframe before it. Only when the keyframe’s keytime is reached does it apply its own value and it does so instantaneously. The value (or time) curve would therefore be a flat line with an immediate vertical step at the keytime of the Hold In keyframe.