Slug Defence Collar using copper mesh

Copper is noxious to molluscs but harmless to humans and shelties, therefore it makes a great alternative to chemical methods of slug control. 

But the familiar, smooth copper tape is little deterrent to the biggest hungry slugs, who slither across with barely a wince. Their slime layer maybe helps insulate them from the copper.

Now : confronting them with spiky copper wires - this changes the game! 

Here I've used a pre-made copper mesh with the following spec, and it works well. 
A slightly lighter gauge would probably suffice too.
   Aperture: 1.23mm
   Wire Diameter: 0.35mm
   Mesh No.: 16 Holes Per Linear Inch
  https://www.ebay.co.uk/itm/133824172841?var=434393535815 

Suggestions : 

• The clips that join the two collar halves together have been designed for compactness, and they're a bit fussy about the diameter of the object they clamp around. This should ideally be the nominal diameter “Ds”. If there's a gap then the the collar is likely to come unclipped. 
  Wrapping a smaller, or non-round, object (e.g. a plant stem) with a few turns of some thin foam sheet, or similar, can help to prevent loosening of the collar.
   
• As with any barrier type defence, check regularly to ensure that debris, overhanging plants, etc. don't provide a bypass route. If there's a way in, the slugs will find it!
   
• Collars with Ds=18 and Wc=6 can be used with my propagator tray legs.

Further Variants :

Can be made via the FreeCAD Parametric source model included

Using the spreadsheet embedded in the model tree, it's possible for FreeCAD users to generate additional variants with different diameters, width, groove etc. 

Refer to the key in the diagram, and edit the corresponding spreadsheet cells (coloured yellow).

Note: The 3D model will (by default) attempt to update itself after each cell edit. When editing several cells, this might cause the model to “fail” partway through due to incompatible combinations. Often this resolves itself when all edits are complete, but this might not always happen. 
Another reason for the model failing is if a parameter is changed by a large amount.
Check for red markers in the model tree which indicate a failed geometry. Beware that a failed model will might present a 3D of the last good geometry, and which is now different to the present spreadsheet content.
In case of a failed model after all spreadsheet edits are complete, re-load the original model and try changing the cells this time in a different sequence, and/or in small increments.