Does a matching column have to be face up?
Yes. All three equal cards must be revealed in the same vertical column before it is removed.
Answer in context
Two visible 6s with one hidden card are only a potential match. The hidden card cannot count until it is legally revealed or replaced.
Two 4s are face up in your left column and the third card in it is still face down. Even if that hidden card is a 4, the column stays where it is. Reveal it on a later turn and all three are face up together, and only then does the column come out.
Do not assume a hidden card matches because it came from the same part of the deck.
This answer is for Classic Skyjo unless stated otherwise. Action and Junior may use different mechanics, and Voyage follows the original Classic gameplay.
Written in our own words and checked against the official rulebook. Skyjo.co.uk is an independent guide, not affiliated with Magilano. Spot an error? Tell us and we fix it.