Three short lines, and that's the whole poem. The speaker simply states that they applied for a job as a security guard. There's no explanation, no reaction, and no hint of whether they got the position. That bareness is what makes it interesting.
Because the poem gives us so little, we fill in the gaps ourselves. The flat, matter-of-fact tone could suggest resignation, as if this is a job taken because nothing else was available. It could also read as quiet honesty, a person admitting where life has led them without dressing it up. A security guard's work is about watching and waiting, guarding things that belong to someone else, and that may hint at a life spent on the edges, observing rather than acting. The line breaks, with "a job as" hanging at the end of a line, slow the sentence down and add a small pause of hesitation.
The mood is subdued, a little wistful, and understated. Nothing is dramatic, yet the plainness leaves a lingering sense of ordinary disappointment, or perhaps ordinary hope.