Complex sentence: Both were based on a heavy elastic warp thread wound around with a much less elastic weft thread forming a netting--the terms warp and weft are used loosely here, the material was not woven using traditional means.
Split into simpler sentences: Both were based on a heavy elastic warp thread with a much less elastic weft thread to form a netting. The terms warp and weft are used loosely here, as the material was not woven using traditional means.