Rule of Seven

The "Rule of 7" is one of the building limitations of RA2 building : you can't possibly build a bot that has more than 7 components in a row (It can be broken with BFE however). It was most likely implemented in the game to reduce lag from huge setups on a single anchor.

Example - you put a baseplate anchor on your chassis, an extender on it, another extender attached on that extender, and repeat this 4 times. The game won't let you attach another component to the last 6th extender, because the setup has 7 components in a row (Anchor-Extender-Extender-Extender-Extender-Extender-Extender)

Another more practical example is the setup on a 36-weapon HS. It is usually:

Snapper II - Extender - HP Z-tek -Tribar - 20cm round extender- 20cm round extender - Mace(or iron spike)

That means: one of the limitations of building a classic 36-iron (or mace) is the need to attach all weapon motors on the direct extender attached to the snapper, the other remaining AP can be used for the drive motors.