A tape-in sandwich is two tabs and a thin section of natural hair. Too much hair and the tab cannot close. Too little and the weft is hanging off a few strands. Both fail. Both look like “the tape was weak.”
Work on clean, dry hair with no oil at the roots. Section horizontally. Place the lower tab under the natural hair, the weft on top, the upper tab closing the sandwich. Press — actually press — with an application tool. Fingers are not a press.
Stay a finger’s width off the scalp. Closer than that and every brush is traction. Further and the weft shows when the hair parts.
Wait 24 hours before washing, working out hard, or swimming. The adhesive needs that set. Skipping it is the most common DIY mistake we hear about.
If you have never sectioned the back of your own head, this is a stylist job. The Complete System includes a guide because the method is learnable. It is not a substitute for a first install you cannot see.