The MT-1 Multi-Tool is an incredibly useful tool that combines most of the tools required for doing layouts into one combination tool: it contains an 8:1 dovetail saddle square, a 6:1 dovetail saddle square, a regular straight saddle square, and a stainless steel sliding T-bevel blade which can be used to transfer angles or mark out dovetails at custom angles. The sliding bevel blade has a very good cam-lock, which is very effective at locking the blade in position, with relatively little force required to lock and unlock - this makes it ideal for use by weak or arthritic hands.
Both the dovetail and straight saddle squares are hinged, so they can be used on corners that aren't 90° angles. There is a v-notch in one end of the blade, which can be used with a pencil or scratch awl to mark a line parallel to an edge.
The MT-1 Multi-Tool is 7.875" (200 mm) tall with the bevel blade parked in the handle, 0.875" (22 mm) wide, and 1" (25.4 mm) thick, and is precisely machined from anodized aircraft aluminum. The longest leg of the sliding stainless steel blade is 7.75" (197 mm) long. This combination of materials won't rust which reduces the maintenance compared to steel and iron tools.