I bought 2x4s and sliced him into 1/2" x 1 1/2" strips. You can buy 1x2 furring strips but like the homemade ones. They hold the moisture barrier to the house and will provide the locations of studs for nailing the siding to ... at some point, one day. I bought pressure treated 2x4s since I have no idea how long it will be before siding will go on. Here is a picture of Genie and Leland making strips using a table saw. We later nailed them. Why install furring strips? If driving rain gets behinds your siding, it can drain down without creating a petri dish for mold and mildew.