If you need to drill or screw right up against something, sometimes a right angle attachment is the only way to do it. But if you are using your impact driver and a long screw, you need something that can hold up to all that torque. DeWALT's Impact Ready Right Angle Attachment might be your answer.
DeWALT sought out to fill what they determined was a gap in what was currently being offered, which was cheap right angle attachments that couldn't hold up. What they built was the DWARA100 Impact Ready Right Angle attachment. It is only 1.75-inches in length, offers a true 90-degree angle, and a floating ring magnet that holds and aligns both the bit and the fastener.
At only $25, the DeWALT DWARA100 will be hard to pass up. The only other quality option is from Milwaukee and costs double the price. Milwaukee's attachment is also not rated for use in an impact; though that hasn't stopped me from trying.