**6. Conclusions**

The proposed tools for detection and/or assessment of the locking phenomena are capable of the detection of the shear locking and shear–membrane locking as well. These tools are also capable of recognizing the problems without locking phenomena present.

The removal of the locking phenomena by modification of the initial mesh, based on the optimized value of the longitudinal order of approximation *p*, can effectively lead to the admissible error value in the final mesh. This may be possible neither in the case of mesh modification based on the maximum value of *p* nor in the case of the standard *hp*-adaptivity.

The elaborated tools are perfectly suited to the adaptation based on approximation error control employing, e.g., the equilibrated residual method of error estimation and the three-step *hp*-adaptive strategy. One may also consider application of these tools as the first step of the adaptation based on iterative diminishing the interpolation error.

**Author Contributions:** Conceptualization, Ł.M. and G.Z.; methodology, Ł.M. and G.Z.; writing and verifying software, Ł.M. and G.Z.; validation, Ł.M. and G.Z.; formal analysis, Ł.M. and G.Z.; investigation, Ł.M. and G.Z.; resources, Ł.M. and G.Z.; writing–original draft preparation, Ł.M. and G.Z.; writing–review and editing, Ł.M. and G.Z.; projects administration, Ł.M. and G.Z.; funding acquisition, Ł.M. and G.Z. Both authors have read and agreed to the published version of the manuscript.

**Funding:** This research was partly funded by Scientific Research Committee Poland under research grants 7 T07A 004 14 and 5 T07A 040 24.

**Conflicts of Interest:** The authors declare no conflict of interest.
