If you (like me) are using a mod that replaces Stone Wall & Metal Wall (Corrected Structures) You may want to remove the Engram Prereq from these walls.

Here's an example that removes the prereqs, sets level requirements to 20 (stone) & 35 (metal) and sets point cost to 10.

OverrideNamedEngramEntries=(EngramClassName="EngramEntry_MetalBehemothWallB_C",EngramHidden=False,EngramPointsCost=10,EngramLevelRequirement=35,RemoveEngramPreReq=True)

OverrideNamedEngramEntries=(EngramClassName="EngramEntry_StoneBehemothWallB_C",EngramHidden=False,EngramPointsCost=10,EngramLevelRequirement=20,RemoveEngramPreReq=True)