[Pen gesture] Hold-through [Mouse action] Left-click [Event messages] ISG_TAP sent when pen is lifted. [Mouse messages] WM_LBUTTONDOWN and WM_LBUTTONUP sent when pen is lifted. Left-click for a long time. No mouse equivalent exists. This is a fallback for when a user performs press-and-hold for a long time. The event reverts to being a tap. [Pen gesture description] 
Tap the screen and hold until the mouse icon appears and disappears. Users are likely to do this when they accident-tally press and hold and want to revert to just tap.