Hedgerow cutters, the solution to tanks being more vulnerable when climbing over hedges and getting shot in the lesser armored underbelly, were all innovation and adaption - and genius foreplanning

The Ordnance units had time to improvise several field expedients to help the infantrymen break through the hedgerows.

The First Army's heavy shop battalion, the 25th, manufactured a number of devices requested by the combat commanders including a simple type of periscope for peering over the hedgerows, and, most important of all, an attachment to enable tanks to penetrate the hedgerows.

By mid-July, budding inventors in the First Army had produced several devices to be attached to the front of a tank to dig into the hedgerows. The best was contributed by Sgt. Curtis G. Culin, Jr., of V Corps' 102d Cavalry Reconnaissance Squadron, a light tank unit. The contrivance itself, a strong iron fork with five straight tines, was developed by an officer of the squadron's maintenance unit, Lt. Steve Litton, who used the angle iron bars or tetrahedrons that the Germans had emplaced off the beaches to rip the bottoms out of landing boats.

 At a demonstration attended by General Bradley and Colonel Medaris, the hedgerow cutter, or Rhinoceros, showed that it could slice through the matted roots in the embankments, enabling the tank to pass through the hedgerow instead of climbing it. The vulnerable underbelly of the tank was not exposed, and the nose was down, so that the guns were in a better firing position.

Beyond the Périers-St. Lô road the armor had to cross a belt of hedgerow country- the hilly, true bocage- before it could get to the plains beyond; it was essential that the tanks get through the bocage quickly. Bradley ordered Medaris to put hedgerow cutters on as many COBRA tanks, light and medium, as possible.

Medaris organized a large crew of welders and skilled mechanics from his maintenance companies, pooling their facilities for mass production, and sent his tank transporters to the beaches to round up tetrahedrons. They were plentiful enough.

The critical item was welding material. Medaris had requisitioned what seemed to the supply agencies enormous amounts of it during the preparations for OVERLORD. Experience had taught him that it would be needed by the service sections of his maintenance companies because they would have to do a great deal of manufacture whenever the inevitable crises in supply arose.

With the backing of Colonel Wilson, the First Army G-4, he not only cleaned out all the welding rod in the depots in England, carrying to the Continent every pound he could, but he took action to increase the supply. His foresight was rewarded. When he flew back from Normandy to obtain enough welding rod to make the hedgerow cutters, it was available.

The evening Medaris left for England, a sudden and acute shortage of oxygen-acetylene cylinders was discovered. Though scarce in the United Kingdom, the cylinders were rounded up and delivered by air before breakfast next morning, an operation that was watched with amazement by Montgomery's chief of staff, Maj. Gen. Sir Francis de Guingand, who was visiting at Bradley's headquarters at the time. In forty-eight hours First Army Ordnance men made nearly 300 hedgerow cutters, and in a week three out of every five tanks to be used in the breakthrough were equipped with them

https://history.army.mil/html/reference/Normandy/TS/OD/OD14.htm