What are dowel holes?

Never heard of them until I read this Clevite 77 bearing guide:

H series bearings have a medium level of eccentricity, high crush and rod bearings have a
hardened steel back and thin overlay. These bearings also have enlarged chamfers for greater
crankshaft fillet clearance and are made wi
thout flash plating for better seating. Bearings with
.001” extra clearance are available for standard size shafts and carry the suffix “HX” (X = extra
clearance). Rod bearings are available with or without dowel holes (HD = with, H = without),