Question

which must be installed halfway between the top of the guardrail and the work surface? top-rails mid-rails toe-boards wire mesh

Explanation:

Mid - rails are installed halfway between the top of the guardrail and the work surface. This is a standard safety requirement in construction and work - at - height scenarios. Top - rails are at the top of the guardrail system. Toe - boards are at the bottom, near the work surface. Wire mesh is a different type of fall - protection material (usually used as a barrier but not installed in the middle position described).

Answer:

Mid - rails