However, it may be best to hide the items from eyes in the post service, and boxes stack easy on a shelf, cylindrical bottles on their side don't .
Bottles are slow to fill with screws though a small top hole, it is better widened. If posting with a reused bottle only , its best to use a 2L water / pop bottle as they are stronger.
Although not ideal, we recommend for strength, the use of fibreglass reinforced tape for strength in this case of sealing lone bottles sent through the post
On the plus side, cardboard is recyclable. The plastic bottle inner can also be used as a screw holder to take to the job in hand and will not get soggy in the rain like a card box if used outside
Taped lid plastic / wax covered paper coffee cups with lids can also be used to hold screws, then inserted into the box (not pictured) though they will not be as strong as the bottles IMO
Top - 4l milk bottle with top cut off , then top folded in to seal opening
Middle - Same as above but more top cut off (4 slits can be cut in sides at top to aid folding )
Bottom - Top cut off 2 water bottles, top then folded over .
Parts cut from bottles (find another use ? )
(screws not shown)
For sharper / heavier contents, a second bottle base sleeve on the other end is used 4L & 2 L shown
Contents shown apart
2 Litre water bottles, cut almost in half, then inserted inside each other.
Plastic cap is left on (not shown in pic)
For a slightly smaller box. the bottle is cut almost in half, then cut again around the bottom of the opening stem.
A plastic coffee cup lid is placed inside the cut open top to stop screws falling out inside the box
A pop bottlte cut in half,
one fitted inside the other
drill or use a hole punch to make 2 holes in the side
Tie 2 used straws together, then thread though holes and tie straw ends together
If there is concern of straw pulling through the holes, the top edge of the bottle can be folded over &
holes drilled through 2 layers