Abstract: A backpack includes: a body including a front panel and a rear panel; a shoulder strap attached to the body and having an adjustable length; and a retention mechanism attached to the body and movable between a first position and a second position, in the first position the retention mechanism being disposed to define a compartment to hold an object and to inhibit first motion of the object toward a bottom of the backpack, to inhibit second motion of the object toward a right side of the backpack, to inhibit third motion of the object toward a left side of the backpack, and to inhibit fourth motion of the object away from the rear panel over a length of the retention mechanism, in the second position the retention mechanism providing an opening to the compartment, the opening extending a majority of the length of the retention mechanism.