The Tightline Trend A make-up artist technique: lining the waterline, to create the look of fuller lashes, with no gaps. Eyes look bigger, wider and beautifully sculpted. How to Tightline with the Lash Sculpting Comb-Brush 1. Tightline with the outer bristles. Gently press the brush on your waterline, filling in between the lash roots, just like a liner would. 2. Define with the inner bristles. Sculpt out and define even the smallest lashes, charging them with volume from root to tip. Reveal a sculpted lash look from every angle.