或见这段文字说明。其中level 就是水平仪量水平。 http://www.diynetwork.com/how-to/rooms-and-spaces/garage/how-to-install-a-garage-door
Step 2 Set the Bottom Piece Into Position
Insert the bottom piece into the door frame, and use a level to properly set the piece. Once the piece is in place, tap nails partway into each jamb. Slant or slightly bend the nails to secure them in place. Use the manufacturer's instructions to assemble the vertical, curved and horizontal pieces of the track and set aside.