• It should NOT BE USED in the BROOD AREA! 
• It should NOT BE USED as an upper entrance in the fall or winter. 
• It should not be used between supers of FOUNDATION (which is far different from DRAWN COMB). 
• The shim should never be in contact with a queen excluder! 

The proper use of a shim is as follows: 

• Use with supers of DRAWN COMB only. 
• Put 2 supers over the queen excluder, then add a shim
• Add a 3rd and a 4th super, then add another shim
• Add a 5th super, install the inner cover that has an upper entrance made into the edge of it, and top this off with the telescoping cover and a brick. 
• The shim is 3/4" inch high, and its placement is defying the "rules" of BEE SPACE, and bees will build BURR comb on top of frames if the shim is used IMPROPERLY, particularly if it is used in the brood area. 
• If the shim is placed between supers of FOUNDATION, the bees (having no construction blueprints) will build burr comb within the 3/4" inch space of the shim, and "weld" the upper super to the lower super with burr comb as they draw foundation. 

I (George Imirie) have been using my shim for 30-40 years on all my colonies supered for extracted honey production with little or no burr comb construction; and it materially helps in the two things I designed it to do: Aid in swarm prevention because it relieves brood chamber congestion from forager bees, and increases honey production because foraging bees can enter and leave the colony via the shim entrances directly into the super area faster than using the bottom board entrance. Install shims when supers are installed, and remove shims when supers are harvested.