In signal circuitry, clearance is the distance from an edge shooter output lane to the last unobstructed lane adjacent to the edge-shooter circuitry. For example, an Fx119 inserter has an unusually high 27hd clearance.
Also, oscillator and eater variants may be said to have better clearance if they allow gliders or other signals to pass closer to them than the standard variant allows. The following high-clearance eater 1 variant by Karel Suhajda allows gliders to pass one lane closer on the southeast side, than is allowed by the standard fishhook shape:
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This is considered to be a variant of the eater 1 because the reaction's rotor is exactly the same, even though three cells in this variant are too overpopulated to allow a birth, instead of underpopulated as in a standard eater 1 glider-eating reaction.