a square bottom plastic bag is designed to stand upright when opened . the bags are constructed with open tops , side handle openings and attached headers or with t - shirt style handles . the bags are produced in registered bag stacks and include means for adhering a rear surface of one bag to a front surface of a subsequent bag to make the bags self - opening when used with a dispensing rack . the headered bags have tear - off headers or headers with weakened areas that will rupture upon dispensing . the t - shirt bags have apertures through the handles to suspend the bags on a rack or a header attached above the handles . the bags have detachable or rupturable center tabs . the bags are registered with hot pins or cold stakes through an upper portion of the bags or bag handles . the bags have openings , microperforations , or are formed of porous material to dissipate heat or moisture .