This study is an investigation of how semantic and syntactic properties interact in a regular way in variants of a common expression type or Snowclone. Conventional variants of this construction are (someone is) a few (French) fries short/shy of a Happy Meal, (someone is) one sandwich short of a picnic and (someone is) one card short of a full deck. All the instances of the expression examined here have the same structure: X (be)(quantifier) Y short/shy of Z. The research questions used when analysing this construction are the following: What are the specific semantic and syntactic properties found in the expression X (be) (quantifier) Y short/shy of Z? What characterises the interaction between these properties? Is there any significance in how they interact for the meaning expressed by specific examples of this construction? The focus is on variants of the construction which have the same or quite similar idiomatic meaning. These are part of an expression group called “Fulldeckisms”, and they are used for stating that someone is mentally inadequate, mildly insane, or that something is not up to standard in a euphemistic and humoristic manner (Moon 1998, p. 159). The context in which the expression is used is important for its regularly metaphorical interpretation. However, what is interesting is that the construction itself appears to be an equally important recognisable factor for this metaphorical interpretation. The formulaic construction, previous cultural knowledge, and a certain level of cognitive ability are required for users of English to interpret the metaphor. The variants discussed have different literal or source meanings, but they all have the same kind of figurative or target meaning. The literal meanings cover a wide range of discourse or cognitive domains. However, the specific source domains appear to be almost irrelevant for forming the figurative meaning as long as the constraints on certain semantic and syntactic features of this expression are observed. Keywords: metaphor, source meaning, target meaning, meronymy, snowclone, construction, valence