A high speed parallel manufacturing line for manufacturing insulated glass units, the manufacturing line including a gas filling topping press that mates a spacer applied lite supplied to the topping press and a topping lite supplied to the topping press to create an insulated glass unit and fills the insulated glass unit with a non-air gas. A heating station applies localized heat to adhesive of the spacer material. A sealing press applies pressure to the insulated glass unit and facilitates further sealing of the spacer material to the spacer applied lite and the topping lite. The line may include a fourth corner sealer that completes sealing of the airspace of the IGU prior to finishing of the IGU.