ALTER TABLE [dbo].[MyTable] CHECK CONSTRAINT [FK_MyTable_SomeCol]

If I script a table with a foreign key, it looks like this:

GO
ALTER TABLE [dbo].[MyTable]  WITH CHECK ADD  CONSTRAINT [FK_MyTable_SomeCol] FOREIGN KEY([SomeCol])
REFERENCES [dbo].[MyOtherTable] ([SomeCol])
GO
ALTER TABLE [dbo].[MyTable] CHECK CONSTRAINT [FK_MyTable_SomeCol]
GO

What is the second part for (ALTER TABLE [dbo].[MyTable] CHECK CONSTRAINT [FK_MyTable_SomeCol])?