within one's shirt coat, robe, etc(He pulled a flask from within his shirt – он достал фляжку из-за пазухи"; "he secreted the money within his robe – он спрятал деньги за пазухойРина Грант)
under one's armpit(The shoulder holster, which keeps the handgun tucked under your armpit. / Shoulder holsters allow you to carry your firearm under one arm. 4uzhoj)
