The message
from "Dave Plowman (News)" contains these words:

I see these in the Screwfix catalogue, Impact Drivers. Anyone know what
that is? Does the drill hammer? Is it just a drill/driver without a
chuck? What is the advantage? Also, Drywall Drivers, also in Screwfix,
what do they do over a drill/driver? If a tool can save me time, effort
and produces a better quality job, then I am always interested.

An impact driver is usually a screwdriver which can take a variety of bits
or sockets and has a cam mechanism within. It's purely mechanical. You
engage it on the screw or nut and whack it with a hammer. Most commonly
used on cars rather than houses.

Until drivels brother posed the question I thought such information was
common knowledge. ;-)

Of course Screwfix may mean something else - if so a reference would help.

They do. Page 634/635 of the current catalogue. Not indexed - Impact
wrenches were which is how I found them.

"Impact mechanism uses rotary impacts to generate extremely high torque"
is the description on the DeWalt jobbie. (Only £249.96.) Seems a bit odd
asking the question in the first place when it is there in black and
white but what would you expect from drivels brother?

--
Roger Chapman