A: Usually, but not necessarily. You should always be putting two clips on the Rule card, but in some cases there are two halves of a Rule you could mark, and you only need to use the decoy spot if you’re only using one half of the qualities listed.

There are just three cards in the base set where the decoy spot might be left unused. Those cards are:

5: A structure must contain at least one:
[yellow/blue/red] [decoy] [block/pyramid/wedge]

26: A structure must contain at least one UNGROUNDED:
[yellow/blue/red] [decoy] [pyramid/block/wedge]

32: A structure must contain ZERO:
[yellow/blue/red] [decoy] [blocks/pyramids/wedges]

So let’s take a look at the first one, and see what kinds of rules we could make out of it, using two clips.

Using the top section and the decoy, we can get:
• A structure must contain at least one yellow.
• A structure must contain at least one blue.
• A structure must contain at least one red.

Using the decoy and the bottom section, we can get:
• A structure must contain at least one block.
• A structure must contain at least one pyramid.
• A structure must contain at least one wedge.

Using the top and bottom sections, with no decoy, we can get:
• A structure must contain at least one yellow block
• A structure must contain at least one yellow pyramid
• A structure must contain at least one yellow wedge
• A structure must contain at least one blue block
• A structure must contain at least one blue pyramid
• A structure must contain at least one blue wedge
• A structure must contain at least one red block
• A structure must contain at least one red pyramid
• A structure must contain at least one red wedge