21.   Plastic doors slid open.

22.   As the train rumbled over a track switch, the subway jolted and tilted a bit, and the door slid open.

23.   Huge iron gates slide open at the mouth of the mine, and guards ask for identification, the reason for your visit, your Social Security number.

24.   When the electric doors to the terminal slid open and the sisters emerged, the screaming, tears and hugging began.