Use one of these for powered solution.
Or one of these for non powered.
Given the price difference I'd choose the powered version. But I'm sure I bought my non powered one from B&Q for £9.99.
hope that helps
Oh one of
these and a protractor will give you the angle.
Here print your own
[img]Download Failed (1)[/img]
better still
this product seems to combine both though it is pricey.