Among the various fittings on the top of the tank is a wing nut like fitting on a 1"NPT opening. The top of the fitting is obviously designed to be finger opened; the attachment which fits into the tank is a 3/16 rod about as long as the tank is deep. There is no marking on the rod, although it looks somewhat like a dipstick. It would be very difficult to read both because the rod does not show the diesel level very well, and one has to tear the boat apart for about a half hour to get at the top of the tank. Any one have an idea what this is? Richard PS the wire attached to what I assume to be the tank level gauge is on another fitting several inches away. --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.241 / Virus Database: 117 - Release Date: 3/27/01