From Quake Wiki
The func_button is a solid entity that is used to create a physical button in the level that triggers events when the player touches it. Unlike the trigger_once and trigger_multiple entities, the func_button is visible and normally used in situations where the designer wants the player to see the button, such as for an elevator button. However, func_button is sometimes used in places that it's difficult for the player to see, such as on the floor to trigger traps, or quite commonly as a means to open a secret area where it must be shot.
The Button tutorial has some examples of the creation and use of the func_button entity.
|Gorgsenegger added a To-Do; Create a func_button tutorial!.|
In addition to the settings listed below, the func_button can be made to move up or down by setting its angle to -1 (up) or -2 (down).
|targetname||The targetname of the button. Since the button is a trigger itself, this is generally used for killing the button from another trigger.|
|target||The targetname of the entity that will be triggered when the button is pressed.|
|killtarget||The targetname of the entity that will be killed when the button is pressed.|
|wait||Time after pressing the button for it to reset and be pushable again. Setting this to -1 will cause the button to stay pressed.|
|delay||Time after pressing the button before triggering its targets.|
|speed||The movement speed of the button.|
|lip||An offset added to the default movement distance that allows the designer to adjust the amount the button sticks in or out after being pressed.|
|health||If set to any value above 0, the button will only be activated by shooting it or hitting it with the axe. Often used for buttons that open secrets.|
|message||A message to display when the button triggers.|
func_button supports standard spawnflags for difficulty and deathmatch presence.
|256||Not on Easy||The button will not spawn on Easy difficulty.|
|512||Not on Normal||The button will not spawn on Normal difficulty.|
|1024||Not on Hard||The button will not spawn on Hard difficulty.|
|2048||Not in Deathmatch||The button will not spawn in Deathmatch mode.|
[ code from entity entry in an .fgd file goes in here ]
This is the definition format used for most old Quake editors, including the original QuakeEd.
[ code from entity entry in a .def file goes in here ]