While this card is on the field: The turn player can Fusion Summon 1 Fusion Monster from their Extra Deck, by banishing Fusion Materials listed on it from their hand or field.
Rulings
Individual Card FAQs
Fusion Monsters Special Summoned without "Polymerization" while "Fusion Gate" is on the field are still considered properly Summoned by a Fusion Summon. So they may be the target of "Monster Reborn", "Call of the Haunted", etc. (This does not apply to Fusion Monsters Special Summoned by the effects of other cards, such as "Magicial Scientist" or "Summoner of Illusions".)
Spell|
Field