What can you do with a dado plane

 Well, a combination plane in my case.

You can cut across the grain!

This is a 3/8" dado in 3/4" thick pine. 

It seats nicely, feels solid.

I found a light shaving is best for dados.  You can take deeper cuts for grooves (with the grain).

The nicker is just protruding from the skate here, below the right side depth stop.

The nickers score & cut the wood grain on the sides of the plane before the main bladed shaves off the wood between.  Without the nicker, you'd tear out the wood.

You could cut both sides with a knife and use a plow plane, but it would probably be faster to do the whole dado with a chisel.

From underneath.  The left side stop (on the right here) is much longer.

This box was made using the 1/4"-1/4"-1/4" method.

• A groove around the bottom on all 4 pieces for the bottom plywood to ride in.
• A dado on the 2 ends 3/8" wide & 3/8" deep
• A rabbet on the sides 3/8" by 3/8".  This is on the side opposite the groove.

The dado/rabbets on the ends and sides should be half the thickness of your stock (3/4" here)

This is usually shown with a table saw and with 1/2" stock.

It's quick, repeatable and strong enough for a drawer that will last for 100 years.  Not everything needs to be dovetailed.