#include <bits/stdc++.h>
using namespace std;
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long t;
  cin >> t;
  while (t--) {
    long long n;
    cin >> n;
    long long x[n], y[n];
    vector<pair<long long, long long> > v;
    for (long long i = 0; i < n; i++) {
      cin >> x[i] >> y[i];
      v.push_back(make_pair(x[i], y[i]));
    }
    v.push_back({0, 0});
    sort(v.begin(), v.end());
    long long flag = 0;
    for (long long i = 0; i < n; i++) {
      if (v[i].second > v[i + 1].second) {
        flag = 1;
        break;
      }
    }
    if (flag) {
      cout << "NO" << endl;
      continue;
    }
    string s = "";
    long long temp = 0;
    for (long long i = 0; i < n; i++) {
      temp = abs(v[i].first - v[i + 1].first);
      while (temp--) s += 'R';
      temp = abs(v[i].second - v[i + 1].second);
      while (temp--) s += 'U';
    }
    cout << "YES" << endl;
    cout << s << endl;
  }
}
