Slug Defence Collar from upcycled electrical cable

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! 

A collar is a compact and affordable defence that can be employed where the slug must climb a narrow stem, leg or post to gain access.

My simplest solution of this kind is  1299198  which employs a pre-made copper mesh that you can buy in sheets.

The type you're seeing now requires a little more effort: worth it if you don't need many collars and could save on buying copper mesh. Most of us have some junk electrical goods waiting for a trip to the recycling centre.

From bits of old electrical wire, one can make satisfyingly imposing obstacles that'll deter even ravenous slugs and snails. 

There's an additional benefit in that the copper elements can be added before the collar is installed, unlike 1299198 where mesh is fastened only after the two collar halves are joined.

Suggestions :

• The design is somewhat adaptable to whatever scrap wiring you can find. 
  Given a selection of copper wires, think about what size of slugs are about:
  Thicker, stiffer wires could stop larger and stronger slugs, and especially snails who might attempt to barge through using the shell.
  But tiny slugs could squeeze through the gaps, and so a spread of many fine wires might stop them better.
  I've provided two sizes of wire hole on most of my collar variants, and tend to alternate stiff wire with stranded wire.
   
• 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!
   
• The collar with Ds=18 and Wb=6 can be used as an alternative on 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, holes 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 still 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.