No, Frog, I don't think I'm making a house rule for shields. The rule for Improvised Weapons is that "An object that bears no resemblance to a weapon deals 1d4 damage (the DM assigns a damage type appropriate to the object)." I tried to explain, in those three paragraphs, how I conclude that the phrase "bears no resemblance to a weapon" does not apply to a shield, and that I think the shield, used as a weapon, should do damage as a mace.
Weapons on the list are, like most entries in the D&D rules, abstractions. Obviously in objective reality you can slash with a short sword or pierce with a long sword, but the D&D weapons list entries are more formal than objective (in the Platonic sense.) You may interpret the rule on Improvised Weapons to require the resemblance to be cosmetic, and that's fine--your ruling is totally valid in your game. My ruling, in my game, is that a resemblance can exist even between things which do not look alike, based on how they would be used as weapons. Hence my comparison between the edge of a shield and the flanges of a mace.
That's my interpretation of the Improvised Weapons rule, and my ruling for my games. The fact that you don't agree with it doesn't make it invalid, nor does it mean that I'm inventing a new "house" rule. There is a tendency here to insist that an interpretation of the rules which is different than the one held by the poster is contrary to the rule itself, and is therefore making up a new rule to contravene it. I'm totally in favor of house rules, but I make a very clear distinction between house rules and table rulings. I think that giving a shield used as a weapon 1d6 bludgeoning damage is a perfectly reasonable application of the published rules.
