In outdoor clothing and bags a technology called seam taping has been around for a number of years and to explain it quite simply it is a process whereby the holes made from sewing two pieces of material together are coated with a sticky or melted plastic tape which ensures that water can't pass through the same holes as the needle did. Taped seams tend to work best where the material has a coating or is able to bond well with the plastic of the tape itself once it is heated, and so is typically seen on materials which are man-made rather than natural. A tape machine is typically a little bit like a sewing machine but instead of having a needle going up and down it will have a roller which is heated that dispenses tape directly onto the material and melts it into place. Our waterproof wet and dry backpacks use this technology because their complicated three-dimensional shape means it is much easier to make them using sewing techniques