The 'yellow sized' terminal crimptool is used to crimp terminals in the gauge 12-10 range.
It is also used to crimp non-moistureproof endcaps and non-moistureproof splices.
We use the AMP 59239-4.
Here's a gauge 12 wire that we are going to crimp into a yellow terminal.

The terminal is put in the crimping head of the tool.

The wire can now be inserted into the terminal.

Like the other PIDG terminal crimps, the wire is inserted and the crimp is made.
Make sure that the rear of the terminal firmly grips the insulation for strain relief. (imagine this terminal to be yellow)

picture by: http://aeroelectric.com/

Now that we have made the crimp onto the terminal we can inspect it.

The terminal.

The crimptool can be set to three different tightness settings. 1 being the tightest.
Looking at the strands of wire we can tell wether the tool should be set tighter or looser.

The tightness can be set by moving the pegs to holes 1, 2 or 3.

When crimping terminals, splices or endacps with this tool, Here are some more guidelines.

Some non-moistureproof splices.

Some endcaps, the red non-moistureproof endcap is crimped with the red terminal crimptool, the blue one with the blue terminal crimptool and the hat shaped one with the endsplice tool. The yellow endcap is not shown here but it's the same principle as the blue and the red endcap.