MOSA

These method plugs patch external calls without having to modify the source assemblies.

These plugs would reside in their own assembly.

This is part of the COSMOS/MOSA collaboration.

Here's an example of a COSMOS plug:

[Plug(Target = typeof(global::System.Math))]
public class MathImpl
{
    public static double Abs(double value)
    {
        if (value < 0)
        {
            return -value;
        }
        else
        {
            return value;
        }
    }
}

More information is available here C# Open Source Managed Operating System - Intro to Plugs

MOSA implementation can use these plug method declaration instead to reduce implementation complexity:

[PlugMethod(@"System.Math.Abs, corlib")]