Background: I have done a scientific project as a part of my graduation program and now I want to present my work through presentation slides. There were some techniques which didn't work and meant I had to employ other techniques. I want to name those techniques on a single slide, but I am unable to find a suitable title for that slide. I don't think that I should use "Challenges" as the title, because I think that that would only be suitable for techniques which posed some problem to me but I managed to solve them somehow.
What should be the title of the slide on which I present the techniques that failed?