Extrude the middle square polygon a reasonable amount (remember, pegs go on both sides of the headstock) then chamfer (0.1 units) the contour edges selected in the image above.
Finally add a MeshSmooth modifier with 3 Iterations to finish the first peg. Use Shift + move to clone the peg. Choose Instance in the Object options.
Next step is to move the pegs in place, three on each side of the headstock.
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