The following photo came out of the DrawTite Hitch Owners Guide. With most typical bathroom scales it can measure trailer tongue weights to 900 pounds. It's pretty straight forward on construction and usage. I would make sure the lumber you use is capable of holding the full trailer tongue weight (4X4) and that the trailer is on level ground and the wheels chocked before trying to weigh the tongue. Also make sure that your scale is capable of at least 250 pounds, preferably 300 pounds. You should be able to measure 2 or 3 times that with this setup which should be applicable for most travel trailers up to 28' in length.