It depends.  Typically no.  If it is an Ameristar brand or other ornamental iron gate, then no.  The supporting framework typically is only 1 ¼" wide and does not have enough surface area to attach to.  Also, the screws included to attach to the gate itself are not self drilling.  If you were able to attach to the gate you would need to predrill a pilot hole in the metal with a 3/16" bit for the screws.  Plus, you will need to check the depth of the material you are drilling into.  The included screws protrude from the True Latch brace typically 1 ⅜” to 1 ¼” inches.  So, make sure your material will be at least that thick. If it is on a welded steel frame gate such as a 1.5” x 1.5” inch square tube framed gate. Or a 2” x 2” inch square tube frame gate, then you would need to do the shovel test. You would need to test to see if the gate gives and is allowed to flex.   With the shovel test or a lever you can check to see if there is flex in the gate frame itself and if the gate frame will flex and lift back to the proper height or a little past the proper height then there is a possibility you could use the True Latch brace after you have raised the gate back to the proper height by the PRE-LIFTING routine. Then after the gate is pre-lifted you would attach the True Latch brace, and then make final adjustments. If the gate metal is made from an Adjust-A-Gate kit, the True Latch anti-sag gate brace will work.  You will be able to attach to the wood 2x4 members that span horizontally.  In summary if you have an Adjust-A-Gate framed made gate, then yes the True Latch anti-sag sag brace can work.  But if a welded metal frame gate then typically no. And, if an ornamental iron gate then typically no.