Publication 2 - Packaging for Mailing - Postal Explorer - USPS.com

Closing, Sealing, and Reinforcing4-2.24 Closing, Sealing, and Reinforcing4-1 GeneralClosing, sealing, and reinforcing are primary considerations in preparing theoutside of a parcel for mailing. The main materials for closing, sealing, andreinforcing mailing containers are adhesives, bandings (strappings), staplesand steel stitching, and tapes (gummed and pressure-sensitive). Frictionclosures, screw caps, and locking devices are used to close and seal cansand similar containers.4-2 Adhesives4-2.1 GeneralAdhesives include glue, paste, cement, mucilage, cold emulsion, and thermalplastic. An adhesive used to close a container is adequate if, when thecontainer is opened, at least a 50-percent fiber tear occurs on the surface towhich the adhesive is applied. An adhesive used on tapes or box flaps mustremain serviceable in temperatures from –20 to 160 Fahrenheit.4-2.2 Box FlapsFor box flaps, the adhesive shouldcover at least 50 percent of the boxflaps and be applied no more than1/4 inch from the box flap ends.Alternatively, four strips of hot-meltadhesive may be used on each part of thebox flap where the outer flap lies over theinner flap, but only if the strips have the following characteristics: Are 3/16 inch wide each (after compression).Are no more than 1-1/2 inches apart (with the first strip no more than1/2 inch from the center seam).Extend to the full width of the inner flap (unless hot-melt adhesive isapplied to 25 percent of the area where the outer flap lies over the innerflap).Publication 2, January 200215