Pinpoint Rafter Location- The Concise Designs patented wire rafter/stud finder provides positive mechanical feedback to locate edge of rafter with an accuracy of +/- 1/16 inch.Fewer penetrations to locate rafter for solar installationsIdeal for composition roofingMade with corrosion-proof materialsSimple instructions: "Thump once, drill once, insert Rafter Finder, measure layout and proceed with confidence!" Follow steps below.Step 1. Place appropriate snap lines on roof to locate horizontal rails.Step 2. Thump roof for best estimate of center location of rafter.Step 3. Drill 5/32" dia. hole roughly 2" left of estimate.Step 4. Raise indicator and insert wire sensor into hole.Step 5. Feed wire sensor through hole and lower indicator.Step 6. Tip of wire sensor below roof is directly below tip of indicator above.Step 7. Rotate knob until wire stops at edge of rafter below.Step 8. Mark center of rafter with soapstone or 3/4" tape from tip of indicator and mark snap line.