Frist, what symptoms does your horse have that makes you wonder if it may have laminitis?
Every horse is different, a horse can founder in 1,2,3 or all 4 feet, depending on the cause of the laminitis.
But generally they will founder in either both front or all 4. Laminitis causes a lot of toe pain as the laminae swells. The clasic founder symptoms are heat in the hooves, bounding pedal pulses, and the founder stance (rocking back onto their heels, trying to releave pressure on the toes). When they walk it appears as if they are being pulled along.
If you suspect laminitis, call the vet & farrier immediately, it is a medical emergency. Not getting immediate care for acute laminitis can cause irreversable damage and in some cases the horse may need to be put down.
Most vets I have worked with will order for the farrier to lower the heel and give support to the frog by putting on pads, then cut the toe way back to releave toe pressure and ease in breakover, then put an open toe shoe on (backwards shoe).
The earlier the treatment the better chance the horse has for a good recovery.