Liners differ from planter in that they are smooth on the inside. They almost always go into some type of structure. An example might be a wooden box planter or into a parapet wall. When requesting a price, specify the opening size and the depth. Length first followed by width and last depth. Round the sizes down to the nearest 1/4". No need to get them too tight. Liners without lips will be about 3/16" smaller that the length and width you specify at the top. Bottoms of the planter will be about 1" short of the top size. This allows us to remove the part from the mold. Wall material thickness in 1/8" nominal, unless you specify them thicker. If you want out turning lips plan on 1 1/2" as a minimum. We can make them wider if you let us know what size you need. Either way just provide the opening size and make the liner to fit.
There are a number of ways to handle the waterproofing of the top edge of a liner. Often “ice and water shield” is used to fold over the upper edge against the supporting wall. Sometimes metal flashing is incorporated. If an out turning lip is used, it goes under a wooden or stone cap. When lining up more than one liner end to end we suggest eliminating the lip between the liners, use a waterproof membrane under a “U” cap. A “U” cap covers the joint and is a good take up or expansion point in a long run. Don’t forget, the end liners might need a lip left on.
I hope these illustrations answer any questions you have. If not, we are at the end of a phone call. Ask us for help.