1) Ascender 2) Skilled worker 3) Someone who ascends on foot 4) Tire shop employee, at times 5) Trained worker 
• (n.) One who mounts. • (n.) An animal mounted; a monture.
Mount'er noun 1. One who mounts. 2. An animal mounted; a monture. [ Obsolete]
[n] - a skilled worker who mounts pictures or jewels etc. 2. [n] - someone who ascends on foot
noun someone who ascends on foot; `a solitary mounter of the staircase`
a person or thing that mounts.