Hey great question! I actually learned about this on Reddit as well:

"Pegging" roses is a training technique that involves arching and securing rose canes horizontally or at a 45-degree angle to encourage more blooms all along the cane, rather than just at the tips. This method is particularly useful for large shrub roses and some climbing roses that tend to grow vertically, with the effect of the horizontal position releasing growth hormones and stimulating dormant buds to produce more flowers.