[SOLVED] Microsoft Project 2019 dependencies

In the 'Precedence' column for C put the task ID for B followed by "FF".
(Sorry for having 2 images - I couldn't find a way to delete the first one to show both the text and the Gantt chart in the one image. )
(I think I have the dependency the way you want it - just put the 'precedence' on the other task if that is the right way around.)
Susan

That doesn't work. I think maybe it LOOKS like yours worked because you had 1day duration for everything. Here's what I got:


It still tries to keep task c an whatever duration is specified, and ignores the 1(FS) constraint

Ah - now you are starting to realise who project managers get paid the big bucks (if only!!!).
What is happening here is that MS Project sees that you have a 1 day Task C that can occur any time after Task A completes but must finish as Task B completes. Because Tasks B is 5 days but Task C is 1 day, MS Project adds the "slack" this creates before the start of Task C.
As with many things, precise wording is important. What I take it you want is for Task C to be of VARIABLE duration but it must start IMMEDIATELY after Task A ends and COINCIDENT with the end of Task B.
(As Task B can start immediately after Task A - there are no other constraints or dependencies that might allow there to be a gap here - it could be argued that Task B and Task C are in fact the same task. However I can imagine situations where (say) Task B is outsourced to a supplier and Task C is some internal process that monitors the progress of the supplier.)
What you probably want is called a 'hammock task' (because it is joined between to 'fixed' points). Some versions of MS Project allow this and others don't. What you need to do (besides looking up 'hammock task' on Google) is to go into the 'Finish' column cell of the proceeding task (Task A in your case) and copy the date (the standard Ctrl-C). Then go to the 'Start' column cell for the hammock task (Task C in your case) and use the 'Paste Special' to select the 'Paste Link' option. That fixes the start of Task C to the end of Task A.
Next go to the 'Finish' column for Task B and copy that as well, then Paste Link it into the 'Finish' column of Task C. This is the part that probably won't work that well for you depending on your MS Project version.
Ultimately, you may need to link the start of Task C to the end of Task A (using the date copy/paste) and then manually adjust the duration to match Task B.
I've not tried it but you might also try setting the 'Predecessor' setting for Task C to be '1FS+0D, 2FF' which can tell MS Project to force the slack to be 0 days - just a guess.
Susan