Highlighted walls are attached, but miss, the highlighted targets

[Anonymous]

Hello to everyone,

I am currently modelling a building in revit 2018, and at the moment I am having some problems about the disposition of one slab. The problem is the error that I am attaining and that you can check by the title and by the picture that I am uploading, with the same name of the title. If someone can help to figure out why this is happening it would be very important to me.

Best regards.

[ToanDN]

It means what it says: the walls are missing the target elements when you are trying to attach the top or base. If their location and boundary are correct then there is no point to attach them. Select the walls and Detach All.