Thrombus is a game based on four square, but designed for three players on a hexagonal court. The hexagon is split into three rhombus-shaped regions, hence the name three rhombus or “thrombus” for short.
Besides the court layout, the main distinguishing feature of thrombus is the addition of a neutral zone in the center, called the wallace.
I hope you will read this page to learn how to play thrombus and then try it yourself with some friends. Below are links to the main sections.
Basic rules
If you have played four square before, this part should be familiar.
The game is played with a ball like this.
I call it a kickball; it looks like in other places it is also referred to as a utility ball.
Three players play the game, each one occupying a rhombus (you can also call them “squares” for short, who cares). The rhombuses are ranked: when you get out, you drop to the lowest rank, and the lower player(s) ascend to fill your spot.
The highest rank has a marked corner, highlighted in the image above. Normally we call this rank the king or queen.
If there are more than three players, the extra players can wait in a line outside the court. When a player is out, they go to the back of the line, and the first person in line takes the lowest rank. The player(s) outside the court can serve as referees in the case of ambiguous or disputed plays.
The highest-rank player serves the ball by bouncing the ball once in their rhombus and then hitting it into another player’s region. The game is like most racket sports: players have to hit the ball when it bounces in their region.
- If the ball bounces in your region and then bounces either inside or outside your region without you hitting it, you’re out.
- If the ball bounces in your region, and you hit it, and it lands back in your region or outside the court, you’re out.
- If you hit the ball before it lands in your region, you’re out.
Some nuances to this scheme will be discussed in the next section. But in general, the goal is to keep volleying the ball into other players’ regions.
Region details
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If the ball bounces on a line, it’s ruled in the hitter’s favor. So if you hit the ball towards me, and it bounces on the line between our rhombuses, it’s considered a fair ball that landed in my region, so I have to play it.
The same applies to outside lines as well. A ball that lands on one of the outer lines of my rhombus is considered fair as well.
If the ball lands on the line between your opponents’ rhombuses, it’s ambiguous. Either player can play it, or neither, and it will be considered a no-fault if no one hits it.
The wallace
The wallace can also be called the walter or the wilson. It serves as a neutral zone to avoid those annoying ambiguous situations when the ball lands in the center.
When the ball bounces in the wallace, it becomes no one’s ball. Anyone can hit it next, but no one is responsible for it either.
If, after bouncing in the wallace, the ball bounces in a player’s region, it becomes that player’s ball to hit, the same as if it had just bounced once in that region.
If, after bouncing in the wallace, the ball bounces out of the court, it is a no-fault.
If the ball bounces twice in the wallace, it can still be played by anyone, but if it bounces into someone’s square without being hit after that second bounce, it’s a no-fault.
If, after bouncing in the wallace, the ball bounces on a line between two players’ rhombuses, it can be played by either player, or left alone. If it bounces out, it is a no-fault.
Miscellaneous rules
A player cannot get out on the first serve. If the server serves in such a way that the other player is unable to hit it successfully, that’s called a bad serve and they have to try again. If you give three bad serves in a row, you’re out.
Case-by-case judgement is necessary to determine what’s actually a bad serve versus a bad receive by the other player. If the other player completely misses the ball of their own accord, that’s generally a redo. If they manage to get a good hit on a reasonably served ball, but it goes out, then that’s on the receiving player, and they’re out.
If the server hits the wallace while serving, they are instantly out. This is known as a wallace death, and it’s the most shameful death in all of thrombus.
If the ball bounces off a player’s grounded foot, it’s usually difficult or impossible to successfully hit the ball. This is called a shoe-shiner and it is considered a no-fault, unless it’s obvious the ball was going to go out if it hadn’t bounced off the player.
If the ball bounces off another part of the player’s body, or a lifted foot, a situational judgement needs to be made. If the ball can be reasonably played after this bounce, you could count it as their hit and keep going. Sometimes, the player might be winding up to hit, and the ball accidentally hits their body first, but they follow through anyway and hit the ball with their hand. If you can keep the ball in play, you may as well, so this kind of thing can be allowed too. Again, if it’s obvious the ball was going to go out if it hadn’t bounced off the player, the player who hit it to them as well.
If a person intentionally hits the ball with a body part besides the hand, it’s usually considered fair. However, purposely kicking or punching the ball is not allowed. Open-handed hits with the palm should be the norm. If you have to kick to save the ball from a tight situation or something, that’s cool.
In general, when you need a judgement call about some play between two of the players, the third player can serve as a disinterested third party. If that player didn’t see or couldn’t tell, you can always call a no-fault and just keep playing. Thrombus is not a competitive game! It’s just for fun, so there’s basically no stakes to any given play. Be nice and keep the ball moving.
You are allowed to intentionally bounce the ball in the wallace multiple times for stylish plays.
Constructing the court
- Hexagon with 6 ft. (1.8 m) sides
- Three lines from center to corners, creating three rhombuses. These lines will also be 6 ft.
- Wallace is a circle at the center with 10 in. (25 cm) radius
- “King’s/Queen’s corner” size doesn’t affect gameplay so it doesn’t really matter. Draw parallel lines something like 1 ft. (30 cm) from the outer lines until they meet.
You can construct the hexagon with a length of rope 6 ft long, using a “compass and straight-edge” method. It’s easier to draw arcs and circles with the rope if you tie loops on either end, one to hold the chalk and one for a second person to anchor. Just make sure that after tying, the loops are spaced 6 ft. from one another.
Pick a center point.
Draw a light circle centered at that point, just light enough that you can see it. You don’t want it to be too strong, because it won’t be part of the final court.
Starting anywhere on the circle, pick a point and draw a small arc 6 ft. away from it. These will be the first two corners of the hexagon.
Add the next two points in a similar fashion, using each new point as the anchor for the next one.
Draw the last two points starting from the first point again. This reduces the total amount of error in the arc-drawing process.
Now you can lay the rope flat to use it as a straight-edge. It helps to have two people hold it tight on either end so it’s straight, while a third one draws. Connect each pair of points to form the hexagon.
Add the three inner lines to form the rhombuses.
Add the wallace in the middle. Here, it helps to have an extra 10 in. length of rope with loops as well. You can anchor it in the center and then use it to draw the circle.
Add the “king’s/queen’s corner” (it doesn’t really matter if it’s accurate, since it doesn’t affect the game) and you’re ready to go!
