A Trackwalker was a railroad employee whose job entailed walking along 5 miles of track daily looking for any issues along the rail line and fixing them as they appeared. ... They were only allowed to call for assistance from other employees for major projects, such as destroyed bridges or severely damaged tracks.

What does USEE mean?

: one to or for whose use a thing is done or given especially : one for whose benefit a suit is brought : use plaintiff.

What did the job of a track walker involve what was the drawback in this job?

One of the main drawbacks of being a track walker is that there are risks associated with this job as trackwalker have to lay, uphold and repair track for fine-gauge railroad tackle which is used in regular railroad provision or in plant yards, pits, sand and gravel pits, and mines.