An end effector, for adhesively attaching a first part to a second part, comprises a support, a first nozzle, movable relative to the support, and a second nozzle, movable relative to the support. The first nozzle comprises a first-nozzle-body outlet port and a first-nozzle separator plate. The second nozzle comprises a second-nozzle-body outlet port and a second-nozzle separator plate. The end effector additionally comprises a first ultrasonic-sensor roller that is rotatable relative to the support, translationally fixed relative to support, and located between the first nozzle and the second nozzle. The end effector also comprises a second ultrasonic-sensor roller that is rotatable relative to the support, translationally fixed relative to support, and located between the first ultrasonic-sensor roller and the second nozzle.