Matching mosfets - linear servo amplifier (AB)
1st -- matching probably isn't critical for this application. If you buy the FETs from the same source, and they are from the same date code, they will likely be closer than you can measure in a reasonable way.

2nd -- if you are matching them, you probably want to match RDSON -- the on resistance. Connect the gate to (say) +10 V, and measure the resistance between source and drain.  Likely it will be &lt;&lt; 1 ohm, and hard to measure in a straightforward way -- if you are familiar with Kelvin measurements, you could do it that way.