The best boat blinds permit hunters to gaze through the material without having to standup, slide a cover, or pop open a lid to fire or gaze. Build your blind, or buy one, tall enough so that your head, while seated, is not peeking above the top frame. No matter how intricate your blind is, it won't serve its purpose if birds see a row of smiling faces peering at them. Several commercial designs have a main body, cover, and an eye level slit to shoot through from a seated position. In the time it takes to push aside fabric or netting an incoming flock can turn and flee from range.
Blind fabric varies from netting, to burlap, to canvas, and so on.
Military surplus tank netting, with 2 to 4 inch squares, is an affordable and effective material. Tan and green strips are woven into the nylon netting, hence creating the camouflage. Tank netting both conceals and provides openings large enough to see through. Most sporting goods dealers sell burlap and canvas-like material that are either sewn or embossed with camouflage patterns. Both materials provide adequate cover, but are too dense to peer through.