8.23.3 \cline



In an array or tabular environment, draw a horizontal rule beginning in column i and ending in column j. The dash, -, must appear in the mandatory argument. To span a single column use the number twice, as with \cline{2-2}.

This example puts two horizontal lines between the first and second rows, one line in the first column only, and the other spanning the third and fourth columns. The two lines are side-by-side, at the same height.

  a &b &c &d \\ \cline{1-1} \cline{3-4} 
  e &f &g &h 

Unofficial LaTeX2e reference manual