How to Lock and Unlock Locking Pliers

How the lock works

Locking pliers use a cam and lever action. When you squeeze the handles past a certain point, the linkage goes slightly over center and holds itself closed. That is why the jaws stay clamped without you holding the handles.

The adjustment screw in the end of one handle sets how far the jaws close before that over-center point. A small change in the screw makes a big change in clamping force. Knowing this makes both locking and unlocking much easier.

How to lock locking pliers, step by step

The goal is a setting where the handles close firmly with a clear snap, not one that takes all your strength.

• Open the handles fully so the jaws are wide open.
• Place the jaws around the work, such as a nut, a pipe or flat stock. Seat the part deep in the jaws, close to the pivot, where grip is strongest.
• Turn the adjustment screw until the jaws just touch the work. Clockwise usually closes the jaws and counterclockwise opens them, though it can vary by model.
• Give the screw about a quarter turn more so the jaws close a little tighter than the work.
• Squeeze the handles hard until they snap over center. The handles should end up nearly parallel and stay shut when you let go.
• Tug the pliers gently to check the grip before you put any force on them.

How to adjust a lock that is too tight or too loose

If you cannot close the handles, the jaws are set too narrow for the work. Turn the screw to open the jaws a little and try again.

If the handles close easily but do not snap over center, or the pliers slip, the jaws are set too wide. Turn the screw in a little at a time until you need a firm squeeze to lock them.

Adjust in small steps, a quarter turn or less. It is common to need two or three tries the first time you clamp a new thickness. Our best locking pliers page covers why the adjustment screw is worth checking before you buy.

How to unlock and release locking pliers

The release method depends on the design. Most modern locking pliers have a lever or trigger on the inner side of one handle. Press or pull it toward the handle and the lock opens, so one hand can do it while the other holds the work.

Trigger release is listed on the WORKPRO 7 in curved jaw model, both DURATECH models and the SK and DEKOPRO sets in our data. Some other listings, such as the IRWIN 4 in long nose and the Crescent five-piece set, do not list a trigger release, so check the product notes if one-handed release matters to you.

• With a trigger: squeeze the handles slightly to take pressure off, then press the trigger and let the handles spring open.
• Without a trigger: pull the handles apart by hand, or pry the lower handle away from the upper one with your fingers or the heel of your hand.
• If it will not open: turn the adjustment screw out a half turn or so to relax the clamp. The release should then move freely.

Release styles at a glance

This table shows which release features the listings in our data state. Where a field says not listed, the maker did not publish it, so it may still exist on the tool.

Common problems and fixes

A lock that snaps open by itself usually means the jaws are set too wide, so the pliers never go fully over center. Close the jaws a bit with the screw.

A lock that will not release is often under too much pressure, or the jaws are twisted by a load on the work. Back the screw out, and if the work is under tension, support it before opening the pliers so it does not spring free.

Jaws that slip even when locked can point to worn or dirty teeth, or the wrong jaw shape for the job. Curved jaws suit round and flat parts, while long nose jaws suit small fasteners and tight spaces. If you are choosing between tool types, our best pliers page puts several styles side by side.

Wipe the pivots and screw with a light oil now and then, and keep grit out of the threads so the screw turns smoothly.

Safety notes

Locking pliers store a lot of force. When they release, the handles can fly open and the work can drop or spring loose. Keep your fingers clear of the handle gap and the jaw pinch point.

Wear safety glasses whenever you clamp, pull or twist, since a slipping jaw can send fragments or the tool itself toward your face. Do not clamp onto live electrical parts or wiring that is plugged in, and never use the pliers as a hammer. Because the jaws can crush or round off soft fasteners, use a proper wrench or socket when a nut or bolt must stay in good shape.

Frequently asked questions

Why do my locking pliers snap shut with so little effort?

The jaws are likely set too narrow for the work, so the lock engages before the jaws really grip. Open the jaws a little with the screw so the handles need a firm squeeze to lock.

Can I leave locking pliers clamped overnight?

It is fine for short holds, but the stored force can wear the parts and mark the work over time. Release them when you are done, and back the screw out slightly for storage.

Do all locking pliers have a trigger?

No. Some models use a lever or no separate release at all, and some listings do not state it. Check the product notes if you want one-handed release.

Will the pliers lock on very thin material?

Yes, if you adjust the screw so the jaws close just under the material thickness. Flat jaws or a locking C-clamp style may hold thin sheets better than narrow jaws.