The “Howard Flip Restrainer” is a rodent restraint device used for I.V. tail vein blood collection and injection. The unit rests on a sturdy steel base which keeps it from moving during injection. The restraint cylinder is raised from the base in order to provide a more ergonomic working position for the user. Tail vein blood collection can be very difficult in rats and mice. The cylinder allows the user access to both tail veins by use of a hinge which is connected under the cylinder. If the user isses one vein, they can flip the unit over which will allow access to the other vein. The rat unit also features a removable door which allows the user to load the animal forward causing less stress on the rat.