What are they?
They are disks of various sizes that you can add to a print to minimise lift and warping.
When to use
When dealing with objects that you are having trouble with the print staying on the bed but do not wish to use a raft either because it will diminish the surface or be difficult to remove.
The helper disks may be particular helpful if you have warping on one side as you can add as many as you like to help anchor the print to the bed.
How to use
Simply download the helper disks from the bottom of this page or go to Thingiverse to get kandydavins' design for the disks. In your favorite slicer load a model you wish to print and place it on the bed in the appropriate location. Now add as many helper disks as you need to keep the base down. The disks are available in several different sizes and you can choose whatever you think will help. Avoid the temptation to scale them down as they are very thin and your slicer may remove them if they become too thin. You only want the disks to barely touch the model so they are connected but will not affect the finish of the object.
When using tree supports you can place the disks under where the the base of the tree support is generated thus allowing you to print supports without having a raft under your print.
This method is sometimes referred to as adding mouse ears to your print.