How to seal a cardboard box
Before you put anything into a cardboard box, you should tape up the bottom of the box. If you don’t, and only fold the bottom of the box flaps over each other, the box could collapse when lifted. You don’t want your best china in pieces all over the floor! Never interlock the flaps of the box as it reduces the strength of the box.
The quickest and easiest way to seal a cardboard box is to use a handheld tape dispenser, which applies the tape tightly to the box and helps reduce tape waste.
To provide extra protection and ensure all the flaps of the box are sealed, use the letter “H” seal method used by most moving companies. It is called the letter “H” method as once complete, the tape on the box will look like a capital letter “H”. It will also reveal any evidence of tampering with the box because of the quantity of tape that would have to be removed.
Fold two of the smaller flaps in followed by the two larger box flaps.
Using the handheld tape dispenser, seal the edges of the cardboard box going across the whole length of the box where the flaps were closed. When doing this allow an overhang of tape. Fold the overhang of tape to the side of the cardboard box.
H tape both ends of the box as shown in picture