I'm with Kurt, use 1/4" bolts. Carriage head or machine head (round head with screwdriver slot). Myrl, are you thinking 3/8" bolts? 1/4" is pretty standard.

Nylon insert nuts for immovability..I like the wingnut idea, but check them often.

Spacers from hardwood dowels, pieces of hardwood scrap, or 3/8" or 1/2" copper tubing all seem to be popular. Brass or bronze tubing would be pretty if you can find some scrap...probably quite expensive to buy.

Shawn

: It's not fancy, but this is what I did on my Merlin. I used 1/4"
: diameter threaded stainless hex head carriage bolts from Home Depot along
: with stainless washers and a stainless and nylon lock nut to hang the
: seats and thwarts. To make the spacer between the seat and gunnel, I cut a
: section from an 1 1/8" oak dowel and drilled a 1/4" hole in the
: center. A 1 1/8" dowel matched the width of the seat support. I used
: a forsner drill bit to recess the head of the bolt and washer to the
: height of the top of the gunnel prior to drilling it for the bolt. This
: was for appearance only. You'll have to adjust the bolt lenghts to match
: the height of the gunnels and seat frame. Let me know if you have any
: other questions.

: Kurt