Montagu Thumbs are located in The Wellington Park which offers so many great natural features and opportunities for rewarding day walks in close proximity to Hobart. Cache is located at the highest point of the Thumbs a bit over a metre away from a vertical cliff.
The photo above is the view you will get from the cache location looking back to Cathedral Rock. The cache should hopefully be easily found and should not put you at risk or in danger while retrieving it, but please take extra care especially in wet or windy conditions.
The Montagu Thumbs are about 1km(including a few small ups and downs) along the ridge line from Cathedral Rock heading towards Mount Montagu (1063 metres altitude). You could get this cache a couple of ways:
A return walk from Betts Rd via Cathedral Rock would be the shortest approach.
But a far more rewarding approach would be to include it in a longer day walk in the area. Possible easy assess points to start or end your walk would be Betts Rd, Pipeline track at Neika, or even the Pinnacle of Mount Wellington.
Care should be taken in planning your walk if you are not familiar with the area. Conditions on the mountain can change rapidly and collecting this geocache should be approached as a full day walk, so bring appropriate gear and supplies. Have a read of this thread on the Bushwalk Australia Forum to avoid some mistakes made by others.
The way I'd recommend to do it is: park at Betts Rd, walk to the Montagu Thumbs via Cathedral Rock and then continue on to Mount Montagu (Trig Point) which offers superb 360 views. After descending Mount Montagu continue on and take the now well marked (no sign but hard to miss) junction to Wellington Falls, from Wellington Falls head down onto the Pipeline Track. Once at the pipeline track take the track heading down into the valley(along a pipeline), cross the Northwest Bay River and link up with the track taking you back to Betts Road. Or you could ride a bike along the Pipeline track to the Wellington Falls track junction and use that as the start/finish point to walk a loop. I have logged the loop walk(including Norris' Hunt cache on my gps(gpx file), please email me and I'll send it to you if interested
I recommend the Wellington Park Recreational Map available from Service Tasmania as it shows the current walking tracks on the mountain.
I am happy to answer any questions so please ask.