It's basically a rake, but it has a triangular-shaped group of thin, long tines, usually with a bend near the bottom. I may be the only person in the Free World to use that term, but it just always seemed to suit. I tried searching on that term but came up empty. Then I found an article from Popular Mechanics and Item No. 3 on that page is what I was describing. I think you can get the same kind of tool in different shapes. I would suggest a Home Depot or Loew's. You might not find the exact same thing but think of it as a comb. The long somewhat flexible tines will pull out the dead stalks of the grass without breaking the new stalks. Remember to prune the grass down some and then get the prunings out of the plant. Some companies refer to "rake teeth" instead of "tines," but these are not teeth, more like metal or plastic brooms, thus the term I use.