Related Clues:

• Addition shape, sometimes
• Himalayan center
• Building build-on
• Letterhead?
• 90-degree joint
• First in line?
• Many a large desk or sofa
• Square-corner shape
• Building addition of 90 degrees
• Right-angled shape
• 90-degree pipe
• Half-rectangle
• Pipe joint with a right angle
• Dogleg shape, roughly
• Follower of kay