When you buy 'chop', you are buying the exact rabbet size you need, already mitered and ready for joining. This is the most expensive way to buy moulding, but the rails should be flawless and cut to exactly 45 degrees.
'Straight cut' is relatively new in the industry. It refers to buying short lengths cut approximately the size you need. This caters to the framer who doesn't want to have a lot of extra stock, but is fussy about the way the miters are cut. It is less expensive than chop, but more than length.
'Length', of course, is length. That is, you buy full sticks of moulding, usually 8ish feet long. This actually comes in 2 varieties. You can buy 'short length', where you buy just the number of feet needed for a specific order (rounded to the full length size. That is, if you need 12 feet, you will end up buying 16 feet) You can also buy 50 feet or 100 feet or a box, which you keep in stock for future sales.
When you buy length, you get all the flaws that are naturally produced in the factory. But it is lots cheaper to make up for the smaller amount of labor required to fill your order. The disadvantage is that you can end up with lots of pieces that are too small to use, but too big to throw away.
I am not familiar with the term "base' but I miss a lot....
And did I welcome you to the Grumble?
