Paper bags or loose small bottles are hard to reseal repeatedly or carry as a batch. This rack is for measured closed bottles with complete flat cap shoulders, saving a base layer by supporting two levels at the cap shoulders; the lower fork openings have a removable cross bar, keeping the bottle removal path separate from lifting straight out of the upper level. Measure bottles and caps first, and make sure bottles are closed before placing them on the rack.

Listed part dimensions are outer bounds; usable interior space is given in this model's specifications.

The ZIP contains the complete STL and STEP files, a size list and notes. Version 1.0.1 Use the complete set of files of the same version and size for matching parts. Preview colors are for reference only; STL files carry no color.

Ranges are set by this model's structure; each combination must pass the studio's structure checks; matching parts update with the parameters.

1. Before printing, get 6 closed round bottles with flat cap shoulders: body outer diameter 24, bottle height below the cap shoulder 35, cap shoulder outer diameter 30, cap height 10 mm; the underside of the cap shoulder must be complete and flat to support the bottle once screwed tight. Minimum lid diameter 29 mm. Measure the threads, strength and sealing of purchased bottles and caps; local flanges, soft caps or loose-cap bottles cannot substitute.
2. Purchase 1 ISO 4762 M3×10 socket head cap screw and 1 DIN 934 M3 nut. 10 mm under the screw head, 3 mm shank, head diameter ≤ 5.5 / head height ≤ 3 mm, HS2.5 tool; there must be M3 thread from 6.5 to 8.9 mm under the head. Nut AF5.5 / 2.4 mm tall; do not switch to a different standard thickness without measuring. The fixed 5 mm guide seat + 4 mm grip tab stack does not scale with outer size; the 10 mm axle passes through the full nut with 1.1 mm showing, clear of the blind bottom.
3. 2 printed parts in total: 1 one-piece grip-hole rack and 1 cross bar. The 152.6 × 4 × 8 mm bar main section follows the total length; screw holes, guide seats and bottle diameter positions are linked; use files from the same download. Cross bar bottom Z = 27 mm, lower/upper cap support faces Z = 39/88 mm. The metal head takes another 3 mm on the right, about 163 mm long including hardware; 160 × 70 × 138 is the assembled outer envelope of the printed parts.
4. First fit the nut from inside the right guide seat on the empty rack. Tightly closed bottles slide into the lower fork openings from the front and rest on the cap shoulder; closed bottles drop into the round holes of the upper level from above; insert the stop bar from the right until the grip tab touches the guide seat, then screw in the M3 from the right. The metal head is the axial retainer for the stop bar, with no printed threads, springs or hidden fasteners.
5. Taking a bottle from the lower level: hold the rack → remove the M3 → pull the whole bar out to the right (at least 170 mm clearance on the right) → lift the closed bottle 2 mm → move it forward until fully clear (at least 110 mm clearance in front) → lift it away. This keeps the upper level and the other closed bottles in place; 4 mm clear gap between the two levels. The upper level lifts straight off. Take the whole bottle down before opening it; loosening the cap on the rack would drop the hanging bottle.
6. Hold the rear holes and set it down gently upright; the lower cross bar only stops bottles sliding forward; the upper level has no inverted holding mechanism. Do not invert, tip or shake; no transport vibration resistance, lid load or seed freshness is claimed. Cells suit measured bottles of the same shape; no brand bottle interface compatibility is provided.
7. Print the rack base down; the two-level plate, grip holes and guide rod holes have overhangs; check supports when slicing and clear supports inside the holes. Cross bar printed 8 mm high with its bottom face down. Test-print the cap support hole/guide rod clearance first, and check that your own bottle caps are flat and the screws can be fitted and removed; check slicing before printing; before use, test-fit and check the carrying load.

Import into your slicer in millimeters and check build volume, orientation and supports for each part. Test-print lids, drawers and connectors first, and print the full set once the fit is confirmed.