At Tanner Bolt & Nut, we field a lot of calls from customers trying to find the right bit or screw type.
To help, we prepared this guide to screw head types and drives.
Click on the image that looks most like the top of the screw head to see the bit you need.
Always use the right driver for the screw head you are working on. I know some of these look the same (can you tell the difference between a Pozidriv and a Phillips from 10 feet away?) but they are not – and you risk damaging the screw and ending up taking a lot of time to extract it if it gets damaged.
This is the original screw drive. You find these everywhere, though the practice of using screws with slotted drives is on the decline because the screwdriver slips out of the slot, particularly when you are applying heavy torque to really tighten down (or loosen, for that matter) these types of screws.
This screw drive type is very popular – and again, you find them in a very wide range of applications. Common sizes are Phillips #1, #2 and #3. The most common Phillips size is #2.
See our available Phillips bits
Not very common, but when you need one, you need one. Same shape and sizing as Phillips, but the screw includes a tamper-resistant pin in the middle. This screw is not used in high torque applications as the design is not very strong and the bits cannot be manufactured to high strength specifications.
A combined Phillips and square recess drive.
This screw head isn’t seen very often in the U.S.A., though it is very common in Europe. It looks a lot like a Phillips screw head, but it includes 4 more contact points. Common sizes are Pozidriv #1, #2 and #3.
Square recess is being used more and more as they are very resistant to cam-out, which is a fancy way of saying the tip of the tool does not slip out and mar the screw head very easily. Commonly found in two sizes: Square #2 and #3.
See our available square recess bits
Square Recess Tamper-resistant
Same design and sizing as square recess, but includes a centered tamper-resistant pin.
TORX, the funny looking screw drive. Well, you see them in a lot of electronics here in the US, and they are gaining ground in a variety of their applications. They range in size from T5 through T55 in 1/4″ insert bits and power drive bits.
Tamper-resistant TORX has a small post in the middle of the drive that prevents a regular TORX driver from working.
See our available Torx tamper resistant bits
TORX Plus is an enhanced TORX design that allows more contact area between the driver and the screw head allowing more torque to be applied, even at high driving speeds. This is a fairly new design.
Tamper-resistant TORX Plus
Tamper-resistant TORX Plus is a licensed design, only available after the purchaser has completed paperwork indicating their authorization to purchase these bits. This design is used extensively in correctional facilities and in other high-security applications. It is different than the usual TORX Plus because it uses only a FIVE lobe design, with a center pin.
The tools to access tamper-resistant hex are limited from general distribution in order to protect equipment from access by end-users. Similar to tamper-resistant TORX, there is a small metal post in the middle of the screw head that prevents a normal hex driver from engaging. Tamper-resistant hex come commonly in the following fractional sizes: 1/8,3/32, 3/16,1/4 and 5/16
See our available hex tamper resistant bits
This unusual three-leg design of the Tri-Wing comes in 3 sizes: #1, #2, #3. We don’t see these too often, though they are available as part of our Master Security Bit Kit.
See our available Tri-Wing bits
Sometimes also known as “snake eyes” and “notched.” Though our diagram shows two holes in the top of the screw, these sometimes also look like a screw with two notches cut into the edge on opposing sides of the screw. A commonly used screw head to avoid tampering, we’ve seen these used in everything from electronics to bathroom stall doors in public restrooms! Comes in 6 common sizes: #4, #6, #8, #10, #12 and #14.
See our available spanner bits
One Way removal tool
This is a specialized application for sure. A one-way screw is installed using a slotted bit – but since the edges of the slot are ramped in the opposite direction, a slotted bit will not engage to remove the screw. This one of a kind removal bits can be adjusted to fit one-way screws and back them out.
See our available one-way screw removal tool
We offer all of the drives described in a variety of formats – 1/4 inch insert bits, power bits, and as complete screwdrivers. Some drives are not listed in our catalog, please call us at 1.800.456-2658 or drop us an email at via our contact us form to order any of these drives individually.