The subject matter of this specification can be embodied in, among other things, a thrust reverser tertiary lock apparatus that includes a probe affixed to an aircraft engine frame and having a shaft having a barb at a first end and configurable to a first configuration and a second configuration, and a receiver affixed to a thrust reverser transcowl slider configured to accommodate the barb and having an end wall with an aperture defined therein, the aperture shaped to permit escapement of the barb in the first configuration and prevent escapement of the barb in the second configuration.