Although there is a wide selection of blanks to choose to build on, sometimes you can't find one that fits your needs. Oftentimes you can find a blank with the proper action, but it's not the correct length. Or perhaps the blank is almost perfect, but the action is just a little too slow. In both these instances, you may have to cut an existing blank in order to create the one you want.
As a rule of thumb, you can cut up to 6 inches off the butt of any 1-piece Rodgeeks blank without affecting the action of the blank. Say you like the action and power of our new 8-foot X-Comps, but want the rod to only be 7 feet 6 inches. You can get the 8-foot blank, cut six inches off the butt, and build the rod like normal.
While cutting from the butt is essentially harmless, you have to be more careful cutting from the tip because it's easy to accidentally ruin the action. As a rule of thumb, avoid cutting the tip of any carbon fiber blank. These blanks tend to have fast actions and stiff tips, so even a little bit of cutting can leave you with an unfishable pool cue.
Fiberglass blanks (and composite blanks with fiberglass tips) are safer to tip cut because they tend to have slow actions and soft tips to begin with. It's rarely a good idea to ever cut more than a couple inches off the tip, but if you have a fiberglass blank that is just a little too soft in the tip and needs a faster action, tip cutting is a great way to stiffen the tip and quicken the action.
When you decide to finally cut the blank, it's best to use a hacksaw (or a dremel tool). Put masking tape around the point where you want to cut it, make a mark on the tape where the cut will be, and start sawing.
Keep these rules in mind next time you have trouble finding the right blank for a build.