General Tools and Instruments 840 use of Dowel Centers - Manual (Page 2)

These dowel centers help to make it easy to precisely align
the holes of two pieces of stock to be joined by a doweled
joint—for example, a shelf and each of its supports. They
can be used in conjunction with a dowel jig to show where
the joining holes need to be drilled.
Drill one set of holes with a diameter of 1/4'', 5/16'', 3/8''
or 1/2'' in one piece of stock (see photo). Slip the dowel
centers of corresponding diameter into the holes, with the
sharp points facing out. Then align the two pieces of stock
by hand and press them together. The sharp points will
leave marks on the second piece of stock indicating exactly
where to drill the second set of holes.
To remove the dowel centers, hit the other side of the stock
with a rubber mallet.