To safely put test tubes of various sizes in storage by a method wherein a rim at the bottom part and a rim at the middle part are fitted together for sealing up and the bottom part and the middle part are connected together while a U-shaped indented part is provided at the rim at the middle part for fitting a ram at the cover part therein and the middle part and the cover part are connected together.

In a tray assembly 1, a bottom part 2 is aligned with and connected to a middle part 3 and the middle part 3 is connected to a cover part 4. The cover part 4 includes a rim 7 that is fitted into an indented part of a rim 9 at the middle part 3. A rim 9 at the middle part is successively fitted into a rim 8 at the bottom part 2 for sealing up. In order to combine the bottom part 2 and the middle part 3, the rim 9 at the middle part is pressed into the inside of the rim 8 at the bottom part. In order to combine the cover part 4, the bottom part 2 and the middle part 3 into an assembly, the rim 7 at the cover part is fitted into a U-shaped indented part of the rim 9 at the middle part. Thereby, test tubes in various sizes are safely put in storage, and the apparatus is used, being combined with an automatic test tube handling apparatus.