Just want to know, what are your guy’s/VEX’s thoughts?
Why create a new topic for a specific rule change ???
If you want rule changes, email GDC…
No, it wasn’t more about a rule change as a new product idea (a 3D sizing tool versus a 2D one). Since VEX doesn’t have one, I putting out a new idea and fetching other forumer’s / VEX’s thoughts on it (and maybe information why it hasn’t been introduced yet or why VEX decided to opt for a 2D one).
ok - sorry misunderstood …
from a practical point of view - the on field sizing tool has two features - one, it is visible to teams what elements of their robot is out of size, and second for horizontal expansion works well to have it out and check quickly if it meets requirements. Boxes might not work well for on field sizing checks.
I think the sizing tool allows all teams to see if criteria is met not in proverbial black box :). Also, boxes take more storage space 
Again apologies for not noting new category …
Let me present a theoretical. What if a robot has a shaft sticking out of the drive chassis by 1/4" on the front left. But, another shaft is sticking out of the chassis on the back right. The robot would pass inspection by the 2D sizer, but that robot is not in size. The box presents a solution to that. (Correct me if I’m wrong)
Also, what about a robot in the shape of a non-square rhombus with side lengths of 18 inches? This robot is not <= 18x18 but would pass the 2D inspection tool.
That second one maybe isn’t realistic. However, I agree with @Gigahertz.t that a 3D sizing tool would be better at enforcing R4. And it would be easier for inspectors to use. Slide it on top of the robot, then pull it off the bot.
But, it’s a box… Put stuff in it…
What I do is I lay the tool on the table, put my robot on top of it, and pick up the tool.
It is a little inconvenient that I have to keep rotating it and that when I pick it up it isn’t parallel to the table (causing it to be slightly smaller than 18’’ on the xy plane).
Boxes may be a little harder to see, but a rigid one would not allow a bot over 18’’ to fit in it. But I do lik the laser concept that @jpearman linked as it provides the functionality of a box while being very clear where the robot trespasses.
The original sizing tool had a baseplate to address this situation. I forget which year this was discontinued and why.
If I remember right this style also has a slightly tighter tolerance, we still have one in our club and use it to check our size because we know if we pass with this one we are for sure in size with the newer style.
In San Diego one of the Event Partners had some clear plastic sizing boxes made. They are used at most of our local competitions, as well as Regional Championships. I do think that they help inspection to move faster, as there is no arguing about whether or not a robot is in size, and it is very obvious what parts need to be fixed if it is not. Regional Championships is this weekend so I can take a picture to post later if anyone is interested. There are also traditional sizing tools to check for expansion, and these tools are also used at the fields when necessary.
Actually there is, the only official sizing tool is discussed in R4.a - so if the box is exactly 18x18x18, then it is wrong, it needs to be slightly larger tolerance as described in the red box notes. I could see teams arguing to have the official sizing tool used.
The box is 18.25" square, so robots pass as long as they don’t touch. As previously mentioned, there are also official sizing tools as well, in case a team asks for them to be used, but the boxes are much quicker and easier. This is a very experienced EP who has run regional championships for years. He is very well-versed in the inspection checklist.
EPs have a commitment to excellence and that means assuring using official tools specified in Game Manual during inspection and on-field sizing for referee team.
Good luck at Regionals!