For Gore-Tex clothing, for example, there are special repair kits. The patches usually come in standardised sizes and shapes (round and square), so there is no need to cut them to size – they are ready to use straight away without any additional tools.
Applying the patches does not require any great craftsmanship: first, ensure that the damaged area is dry and free of dirt or other foreign substances, as the patch will otherwise not adhere properly. Smooth out the fabric and press the patch firmly onto the damaged area for a few minutes. If you have patched the hole whilst out and about, you should iron over the patch again at home to ensure it holds better. Alternatively, whilst out and about, you can heat a pan of water and then – using the hot base as a makeshift iron – press it onto the hole to speed up the drying process.
An alternative to patches are adhesives such as Seam Grip. Although these adhesives last significantly longer than patches, they also take longer to dry. With most products, however, you should allow the functional clothing to dry for around 24 hours. Adhesives are therefore not suitable for immediate repairs. The advantage of adhesives, however, is that they can usually also be used to secure loose seams – something that is not possible with patches.